PSYC 210 Chapter Notes -Null Hypothesis, Standard Deviation, Normal Distribution
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Chapter 5 Vocabulary 1
Distribution of means – distribution of means of samples of a given size form a population; comparison
distribution when testing hypotheses involving a single sample of more than one individual
Mean of a distribution of means (µM) – the mean of a distribution of means of samples of a given size from a
population; comes out to be the same as the mean of the population of individuals (µ);
Variance of a distribution of means (δ2
M) – variance of the population divided by the # of scores in each sample
Standard deviation of a distribution of means (δM) – square root of the variance of a distribution of means; also
called standard error of the mean (SEM) or standard error (SE)
Z test – hypothesis-testing procedure in which there is a single sample and the population variance is known
1. Restate the question as a research hypothesis and a null hypothesis about the populations.
2. Determine the characteristics of the comparison distribution.
c. δM =
d. Approximately normal if population normal or N > 30
3. Determine the cutoff sample score on the comparison distribution at which the null hypothesis should be
rejected. Use the normal curve table.
a. One-tailed cutoff at 5% 1.64
b. Two-tailed cutoff at 5% 1.96
4. Determine your sample’s score on the comparison distribution
5. Decide whether to reject the null hypothesis. If your score #4 is more extreme than #3, reject the null.
Confidence interval (CI) – the range of scores that is likely to include the true population mean
95% CI – confidence interval in which there is a 95% chance that the µ falls within this interval
99% CI – confidence interval in which there is a 99% chance that the µ falls within this interval
Confidence limit – upper or lower value of a confidence interval
1. Find the standard error
2. Find the raw scores
a. 95% CI
b. 99% CI
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