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# PSYC 210 Chapter Notes -Null Hypothesis, Standard Deviation, Normal Distribution

Department
Psychology
Course Code
PSYC 210
Professor
Cathy Mc Farland

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Chapter 5 Vocabulary 1
Distribution of means โ 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 (ยตM) โ 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 (ยต); ๎ค๎ฏ๎๎ต ๎๎ค
Variance of a distribution of means (ฮด2
M) โ variance of the population divided by the # of scores in each sample
๎๎ฏ
๎ฌถ๎ต๎๎๎ฌถ
๎ฐ
Standard deviation of a distribution of means (ฮดM) โ square root of the variance of a distribution of means; also
called standard error of the mean (SEM) or standard error (SE)
๎๎ฏ๎ต๎๎ถง๎๎ฏ
๎ฌถ
Z test โ 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.
a. ๎ค๎ฏ๎๎ต ๎๎ค
b. ๎๎ฏ
๎ฌถ๎ต๎๎ฐ๎ฐฎ
๎ฏ
c. ฮดM = ๎ถฅ๎๎ฏ
๎ฌถ
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% ๏  ๏ฑ1.64
b. Two-tailed cutoff at 5% ๏  ๏ฑ1.96
4. Determine your sampleโs score on the comparison distribution ๎ผ ๎ต๎๎ฏ๎ฌฟ๎๎ฐ๎ฒพ
๎ฐ๎ฒพ
5. Decide whether to reject the null hypothesis. If your score #4 is more extreme than #3, reject the null.
Confidence interval (CI) โ the range of scores that is likely to include the true population mean
95% CI โ confidence interval in which there is a 95% chance that the ยต falls within this interval
99% CI โ confidence interval in which there is a 99% chance that the ยต falls within this interval
Confidence limit โ upper or lower value of a confidence interval
1. Find the standard error ๎๎ฏ๎ ๎ต๎๎ถฅ๎๎ฏ๎
๎ฌถ๎ต๎๎ถฅ๎๎ฌถ๎๎ฐ
2. Find the raw scores
a. 95% CI
i. ๎ฎ๎๎๎๎๎๎๎๎๎๎ ๎ต ๎๎ฏ ๎ต๏บ๎ณ๎ค๎ป๎ธ๏ป๏บ๎๎ฏ๏ป
ii. ๎ท๎๎๎๎๎๎๎๎๎๎ ๎ต ๎ฏ๎ต๏บ๎ณ๎ค๎ป๎ธ๏ป๏บ๎๎ฏ๏ป
b. 99% CI
i. ๎ฎ๎๎๎๎๎๎๎๎๎๎ ๎ต ๎๎ฏ ๎ต๏บ๎ด๎ค๎ท๎บ๏ป๏บ๎๎ฏ๏ป
ii. ๎ท๎๎๎๎๎๎๎๎๎๎ ๎ต ๎ฏ๎ต๏บ๎ด๎ค๎ท๎บ๏ป๏บ๎๎ฏ๏ป