# Psychological Statistics Midterm Flashcards

Terms Definitions
 event each unique outcome the mean of binomial distribution u=np Unimodal Distribution only has one hump Mode 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 population the entire collection of events that you are interested in Continuous Scale Allows for fractional amounts; it continues between the whole-number amounts. Z-scores How many standard deviations a score is from the mean, normal distributions range from -3 to +3 power 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 Inferential 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 mean 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. Spread/Dispersion/Variability 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 _______. Beta 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 hyp...it 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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