Psych 382, Chapters 4-6

hypothesis testing procedure

1.- identify the two pop -state the hypothesis *RH *Null 2. determine characteristic of comparison dis. 3. determine the cuttoff sample score on the comparison dis. at which the null hypothesis should be rejected 4. determine the sample' score on the comparison distribution 5. decide whether to reject the null hypothesis

Since the psychologists are now comparing the mean of an experimental group with a known population mean, the appropriate comparison distribution is the distribution of A. all possible means of 30 freshmen. B. freshmen from which the sample was drawn. C. freshmen on whom the counseling sessions had no effect. D. the distribution of means with a standard error of 2.13.

A. all possible means of 30 freshmen.

The psychologists have committed a Type I error when they A. reject the null hypothesis when it is true. B. fail to prove the research hypothesis. C. incorrectly estimate beta. D. use a one-tailed test.

A. reject the null hypothesis when it is true.

When the psychologists set beta for their study, they are A. setting the level of significance. B. establishing the probability of making a Type II error. C. acknowledging the appropriateness of a two-tailed test. D. determining the appropriate comparison distribution.

B. establishing the probability of making a Type II error.

The symbol for the variance of the distribution of means is A. μM B. σM² C. σM D. σ²

B. σM²

Which of the following formulas would be used in calculating the 95% confidence interval? A. M+(±1.64)(SEM). B. M+(±2.33)(SEM). C. M+(±1.96)(SEM). D. M+(±2.58)(SEM).

C. M+(±1.96)(SEM).

To determine whether the difference between the sample mean and the population mean is statistically significant, the psychologists will calculate A. ∑. B. N. C. Z. D. μ.

C. Z.

If the psychologists noted that in one of the experiments they conducted, the distribution of the population expected under the research hypothesis had little overlap with the distribution of the known population, the psychologists had observed A. the use of a liberal alpha. B. the effect of low power. C. a large effect size. D. a practically significant result.

C. a large effect size.

If the psychologists could know that they were making a Type II error, their concern would be that A. the experiment must be repeated to confirm their results. B. they had incorrectly rejected the null hypothesis. C. a potentially useful practice would not be implemented. D. their results would not be statistically significant.

C. a potentially useful practice would not be implemented.

The degree to which the stress scores of students who participate in the counseling sessions differ from the scores of students who do not is an indication of A. experimental effectiveness. B. power. C. the effect size. D. the significance level.

C. the effect size.

Which of the following formulas would be used in calculating the 99% confidence interval? A. M+(±1.64)(SEM). B. M+(±2.33)(SEM). C. M+(±1.96)(SEM). D. M+(±2.58)(SEM).

D. M+(±2.58)(SEM).

The psychologists will calculate the variance of their distribution of means by A. multiplying the variance of the population of individual cases by the number of subjects in the sample. B. subtracting the sample's variance from the population variance. C. taking the square root of the variance of the distribution of means. D. dividing the variance of the population of individual cases by the number of subjects in the sample.

D. dividing the variance of the population of individual cases by the number of subjects in the sample.

The psychologists have committed a Type II error when they A. fail to prove the research hypothesis. B. incorrectly estimate beta. C. use a conventional level of alpha. D. fail to reject the null hypothesis when it is false.

D. fail to reject the null hypothesis when it is false.

The psychologists are said to have made a decision error when they A. miscalculate the student's Z score after the counseling sessions. B. use the normal curve table incorrectly and obtain an incorrect cutoff sample score. C. use a significance level of .10 instead one of the conventional levels of significance. D. reject the null hypothesis when the counseling sessions had no effect on the student's stress.

D. reject the null hypothesis when the counseling sessions had no effect on the student's stress.

(μ1 - μ2) /σ is a formula for calculating A. power. B. sample size. C. raw effect size. D. standardized effect size.

D. standardized effect size.

Statistical power can be defined as the probability A. that the results of a study will result in advances in applied psychology. B. of rejecting the null hypothesis if the null hypothesis is true. C. of obtaining an effect size that will always be significant. D. that the study will yield a significant result if the research hypothesis is true.

D. that the study will yield a significant result if the research hypothesis is true.

If the psychologists report a difference between the student's stress level after counseling and the stress level of students in general and include the notation "p < .05" to describe this difference, they are indicating that A. the result is not statistically significant at the .05 level. B. the sample score falls in either the upper 5% or the lower 5% of the comparison distribution. C. there is a 95% chance that the research hypothesis is true. D. the chance of obtaining this result is less than 5% if the null hypothesis is true.

D. the chance of obtaining this result is less than 5% if the null hypothesis is true.

type II error

Failing to reject a null hypothesis when it is in fact false- concluding that the experimental treatment is ineffective when it does have an effect.

distribution of means

a distribution of all possible means of samples of the same size as the sample in the experiment

effect size

a measure between population means, does indicate the amount of change in the variable being measure after an experimental treatment

hypothesis testing

a procedure for deciding whether the outcome of a study conducted with a sample of participants supports a theory or innovation that then can be applied to a population.

research hypothesis

a statement abt the predicted difference between populations

According to Cohen's conventions for research that compares means, a small effect size would be A. .20. B. .50. C. .80. D. .90.

a. .20

8. The research hypothesis may also be called the A. alternative hypothesis. B. cutoff hypothesis. C. decision hypothesis. D. significant hypothesis.

a. alternative hypothesis

If the psychologists are using the .05 level of significance and find that the observed reduction in the student's level of stress would be fewer than 2 times in 100, they A. can accept the research hypothesis. B. have proved the null hypothesis. C. should report that the results are inconclusive. D. must use a more conservative alpha.

a. can accept the research hypothesis

If the psychologists make a statement about the probability that the true population mean lies between 25.61 and 30.39, the values 25.61 and 30.39 define A. a confidence interval. B. a statistically significant Z. C. the standard error of the mean. D. the population mean.

a. confidence interval

The standard deviation of the distribution of means calculated by the psychologists is also known as A. the standard error. B. the confidence limit. C. a point estimate. D. an interval estimate.

a. the standard error

The values 25.61 and 30.39 are called A. confidence intervals. B. confidence limits. C. point estimates. D. standard errors.

b. confidence levels

When compared to the distribution of scores of all freshmen who have ever taken the inventory, the shape of the distribution of means will A. have more spread. B. have less spread. C. be skewed. D. be rectangular.

b. have less spread

9. The comparison distribution is the distribution that describes A. population 1. B. population 2. C. decision errors. D. conventional levels of significance.

b. pop 2

11. The target score against which researchers will compare their experimental result is called A. beta. B. the cutoff sample score. C. significance. D. the type error score.

b. the cutoff sample score

Since the mean for the population of freshmen who have taken the stress inventory is 36 and the standard deviation is 8, the mean of the distribution of means is A. 8. B. 26. C. 36. D. 64.

c. 36

According to Cohen's conventions, for research that compares means, a large effect size would be A. .20. B. .50. C. .80. D. .90.

c. 80

13. An experimental result is said to be statistically significant when the A. research hypothesis is rejected. B. Type II errors are identified. C. null hypothesis is rejected. D. alpha level is set prior to the analysis.

c. null hypothesis is rejected

10. Comparison distributions may also be called A. conventional distributions. B. cutoff distributions. C. sampling distributions. D. Type I distributions.

c. sampling distributions

12. The conventional levels of statistical significance include A. .10 and .20. B. .05 and .10. C. .05 and .20. D. .05 and .01

d. .05 and .01

By using a sample of 30 freshmen, the psychologists can assume that the distribution of means will be A. bimodal. B. generally rectangular. C. seriously skewed. D. approximately normal.

d. appox. normal

type I error

rejecting the null hypothesis when it is true- concluding that the experimental treatment has effect when it does not.

nondirectional hypothesis( two tailed)

state that one population will be different from the other, but they do not specify whether pop 1 scores will be higher or lower than pop 2 scores.

Directional hypothesis (one-tailed)

states interest in predicting the direction of effect of the experimental treatment, whether the value of the variable being measured will increase or decrease.

null hypothesis

the crucial opposite of the research hypothesis and stated that the means of the population will be different, or if a difference is observed, it will be the opposite direction from the predicted direction.

comparison distribution

the distribution of the variable being measured if the null hypothesis is true, thaat is in the absence of an experimental treatment or if an experimental treatment has no effect.

z-test

the hypothesis-testing procedure used to compare a single sample mean with a population mean when the population variance is known.

statistical power

the probability that a study will yield a significant result if the research hypothesis is true.