Psychological Statistics Midterm Flashcards

Terms Definitions
each unique outcome
the mean of binomial distribution
Distribution only has one hump
The score that occurs most frequently...remember, it is possible to have a bimodal or multimodal distribution.
One-Tailed test
Statistical hypotheses specify either an increase or a decrease in the population mean score. AKA Makes a statement about the direction of the effect
the entire collection of events that you are interested in
Continuous Scale
Allows for fractional amounts; it continues between the whole-number amounts.
How many standard deviations a score is from the mean, normal distributions range from -3 to +3
he probability of selecting a mean from Mean Distribution 2 and having that mean be above the critical value for distinguishing it from Mean Distribution 1
Most statistics in use in psychology are
Internal validity
Measures the extent to whcih the different items within a measure "hang together" and test the same thing
Criterion-reference tests
Measure mastery in a particular area or subject
indicates the point on the scale of measures where the population is centered.the average of the scores in the population. Numerically, it equals the sum of the scores divided by the number of scores.
Indicates how the scores are around the central point. he data values in a sample are not all the same. This variation between values is called dispersion.When the dispersion is large, the values are widely scattered; when it is small they are tightly clustered
hypothesis testing calculates
the probability that the differences are due to random variability (i.e., the first option or the Null Hypothesis)
alpha level
a result is due to chance if probability is greater than the alpha level, it is non-chance if less than the alpha level .. Its statistically significant!
External validity
The extent to which a test measures what it intends to measure (4 aspects of external validity)
an interval scale
he distance between any two adjacents units of measurement is the same but the zero point is arbitrary. eg. temperature 30 degrees more than 40 degreesie. heights of tides, and the measurement of longitude.
the probability of a Type II error is _______.
descriptive statisticsalpha and the number of tails. If alpha = .05 and we are using a two-tailed test, then the critical value is 1.96 (from the Z tables).
the science of describing distributions of samples or populations
standard deviation of a binomial distribution
= sq root of npq
one tail left
prior evidence u less than aHo: u greater than or = to aH1: u less than a
If the t-value exceeds critical value,
the null hypothesis is rejected
type II error
You have committed a this error if you have failed to reject the hypothesis...u thought it was true was not
comparison distributions are used..
are used to compute the probability of the obtained sample result under the assumption that the null hypothesis is true
assumptions of the one sample t-test
1. the sample is randomly and independently selected from the population. 2. the scores on the variable are normally distributed in the population
What happens in Type II error?
No research report is created, Not much loss to the scientific community, Loss to researcher, Other researchers can still find the effect
sampling error, why does it occur
will occur b/c sample data is only based on a portion of the population, so sample stats may differ from the value of its corresponding population parameter
What happens when a distribution is standardized?
Transforming all x's into z scores. Mean of 0. Standard deviation of 1
What does it show if we reject our null?
we have shown evidence that it is likely to be untrue
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