| Terms |
Definitions |
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modified boxplot
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a display for quantitative data that graphs the five-number summary on an axis and shows outliers of they exist
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double-blind
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when neither the subjects nor people who have contact with them know which treatment a subject received
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intersection
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the event that all of the events occur
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monotonic increasing function
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Preserves the order of data. That is, if a > b, then f(a) > f(b)
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probability
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the proportion of times the outcome would occur in a very long series of repetitions
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pth percentile
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the value such that p percent of the observations fall underneath or at it (median is 50th percentile)
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probability model
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a mathematical description of a random phenomenon consisting of a sample space and a way of assigning probabilities to events
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placebo
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a dummy treatment
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five-number-summary
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A summary of a data set that includes the minimum, lower quartile, median, upper quartile, and maximum.
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union
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the event that at least one of the collection occurs
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conditional probability
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the probability that an event will occur given that one or more other events have occurred
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left-skewed
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A density curve where the left side of the distribution extends in a long tail. (Mean < median.)
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monotonic function
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moves in one direction as its argument t increases, Moves in one direction as its argument t increases
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subjects
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what the units are called when they are human beings
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study
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an experiment when we actually do something to people, animals, objects in order to observe the response
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factor
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the explanatory variables in an experiment
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block
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a group of experimental units or subjects that are known before the experiment to be similar in some way that is expected to affect the response to the treatments
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variable
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any characteristics of an individual
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quantitative variable
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takes numerical values for which arithmetic operations such as adding and averaging make sense
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distribution
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tells you what values the variable takes and how often it takes these values
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third quartile
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the median of the upper half of the data
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randomize
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use impersonal chance to assign experimental units to treatments
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right-skewed
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Right tail of a graph is longer than the left; mean > median
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explanatory data analysis
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using statistical tools and ideas to help you examine data in order to describe their main features
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slope
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the rate of change.
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probability sample
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a sample chosen by chance
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lurking variable
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a variable that is not among the explanatory or response variables in a study and yet may influence the interpretation of relationships among those variables
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curved pattern
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shows that the relationship is not linear
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population
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the entire group of individuals that we want information about
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histogram
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a bar chart representing a frequency distribution.
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outlier
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an individual observation that falls outside the overall pattern of the graph
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extrapolation
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the use of regression line for prediction far outside the domain of values of the explanatory variable(x) that you used to obtain the line or curve.
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voluntary response sample
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consists of people who choose themselves by responding to a general appeal
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correlation
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measures the direction and strength of the linear relationship between two quantitative variables.
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monotonic decreasing function
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Reverses the order of data. That is, if a > b, then f(a) < f(b)
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symmetric
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having similarity in size, shape, and relative position of corresponding parts.
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z score
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a measure of how many standard deviations you are away from the norm (average or mean)
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normal probability plot
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a display to help assess whether a distribution of data is approximately normal; if it is nearly straight, the data satisfy the nearly normal condition
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nonresponse
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occurs when an individual chosen for the sample can't be contacted or does not cooperate
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explanatory variable
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a variable that is being manipulated by the researcher in order to see if it affects the outcome variable
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sampling
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involves studying a part in order to gain information about the whole
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exponential growth
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increases by a fixed percentage of the previous total
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dotplot
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a type of graph used to display quantitative data, graphs a dot for each case against a single axis
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undercoverage
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occurs when some groups in the population are left out of the process of choosing the sample
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statistical inference
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answers specific questions with a known degree of confidence
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statistics
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the science of data
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Interquartile range
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Q3-Q1
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statistical significance
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an observed effect so large that it would rarely occur by chance
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random
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when individual outcomes are uncertain
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outlier
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an observation that lies outside the overall pattern of the other observations
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influential observations
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individual points that substantially change the regression line
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bias
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when the design of a study is systematically favors certain outcomes' systematic favoritism towards one outcome.
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time plot
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plots each observation against the time at which it was measured
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trend
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a long-term upward or downward movement over time
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simulation
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the imitation of chance behavior, based on a model that accurately reflects the experiment under consideration
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convenience sampling
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chooses the individuals easiest to reach
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independent
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knowing that one event occuring does not change the probability that we would assign to the other event
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median
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the midpoint of a distribution
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probability model
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Used to calculate theoretical answer.
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density curve
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a curve with an area of exactly 1 (100%) beneath it; alawys on or above the horizontal axis; median divides area under curve in half; mean is the 'balance point'; when mean and median are the same, curve is symmetric
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percentile
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A point on the distributionbelow with a certain % of scores fall. Ex: Scored in the 99th percentile = only 1% scored higher than you
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ogive
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a line graph of a cumulative frequency or cumulative relative frequency distribution.
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observational study
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observes individuals and measures variables of interest but does not attempt to influence the responses
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least-squares regression line
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the line that makes the sum of the squares of the vertical distances of the data points from the line as small as possible
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categorical variable
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places an individual into one of several groups or categories
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standard deviation
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the square root of the variance
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response variable
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measures an outcome of a study
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strata
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groups of similar individuals
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sample space
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the set of all possible outcomes
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block design
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the random assignment of units to treatments is carried out separately within each block
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complement
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the event does not occur
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residual
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the scatterplot of the regression residuals against the explanatory variable
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lack of realism
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the most serious potential weakness of experiments
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event
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any outcome or a set of outcomes of a random phenomenon
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randomization
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the use of chance to divide experimental units into groups
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experimental units
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the individuals on which the experiment is done
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first quartile
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the median of the lower half of the data
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Simpson's paradox
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refers to the reversal of the direction of a comparison or an association when data from several groups are combined to form a single group
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sample
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items selected at random from a population and used to test hypotheses about the population
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census
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attempts to contact every individual in the entire population
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disjoint events
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events that have no outcomes in common
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simple random sample
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consists of individuals from the population chosen in such a way that every set of individuals has a equal chance to be the sample actually selected
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individuals
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the objects described by a set of data
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confounding variables
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factors that cause differences between the experimental group and the control group other than the independent variable
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matched pairs
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a common form of blocking for comparing just two treatments
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seasonal variation
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a pattern that repeats itself at regular time intervals
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joint probability
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the probability of two events occurring together
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mean
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the ordinary arithmetic average or most common measure of center
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intercept
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the value of y hat when x= 0
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tree diagram
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a branching diagram that shows all possible combinations or outcomes of an event
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sample design
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refers to the method used to choose the sample from the population
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scatterplot
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a graphed cluster of dots, each of which represents the values of two quantitative variables.
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transforming/reexpressing
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applying a function such as the logarithm or square root to a quantitative transforming variable
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linear growth
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increases by a fixed amount in each equal time period
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experiment
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A research method in which an investigator manipulates one or more factors to observe the effect on some behavior or mental process
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joint event
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simultaneous occurence of two events; probability is called a joint probability
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treatment
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a specific experimental condition applied to the units
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