PSY-380 Chapter 10

Inferential statistics are used to

a. decide whether sample data accurately represent a particular relationship in the population.

Which of the following null hypotheses would require using a two-tailed test? a. c. b. d.

d.

Jeri has conducted a study on the average salary of recent graduates in her major at State College. She has randomly selected and surveyed 25 recent graduates from her program. The annual average income of this sample of recent graduates is $34,000. Jeri knows that the population mean income for recent graduates in her area of study is $31,000 with a If she uses and a two-tailed test, what is her conclusion? a. Reject and accept . b. Reject and accept . c. Reject and accept . d. Reject and accept .

a.

Which of the following accurately defines a Type I error? a. Rejecting when is true c. Retaining when is true b. Rejecting when is false d. Retaining when is false

a.

Which of the following alternative hypotheses would require using a two-tailed test? a. c. b. d.

a.

If you reject the null hypothesis, which of the following may occur? a. A correct decision or a Type I error b. A Type I error or a Type II error c. A correct decision or a Type II error d. A correct decision or a Type I error or a Type II error

a. A correct decision or a Type I error

Which of the following is called the hypothesis of "no difference"?

a. The null hypothesis

Which of the following is correct regarding statistical hypotheses (null hypothesis and alternative hypothesis)?

a. They describe the population parameters our sample data represent if the predicted relationship does or does not exist.

When choosing between one-tailed and two-tailed tests, a. use a one-tailed test only if you have a convincing reason for predicting the direction. b. always use two-tailed tests. c. use a two-tailed test only if you have a convincing reason for not predicting a direction. d. use the one that is most likely to produce significant results.

a. use a one-tailed test only if you have a convincing reason for predicting the direction.

The Physical Fitness Test (National Level for Girls) shows the national average for 10-year-old girls on "right-angle push-ups" to be = 13. Principal Smyth hypothesizes that her girls at Strong School are significantly above the national mean. If the and the scores for nine girls are as reported here, compute and determine if Principal Smyth is right. Use . 14 16 18 16 12 16 17 20 15 a. , so Principal Smyth is right. c. , so Principal Smyth is right. b. , so Principal Smyth is wrong. d. , so Principal Smyth is wrong.

b.

If and , what is the value of ? a. 2.31 c. -0.38 b. -1.30 d. -2.31

b. -1.30

What happens to the probability of committing a Type I error if the level of significance is changed from = 0.01 to = 0.05? a. The probability of committing a Type I error will decrease. b. The probability of committing a Type I error will increase. c. The probability of committing a Type I error will remain the same. d. The change in probability will depend on your sample size.

b. The probability of committing a Type I error will increase.

Which of the following is true of any one-sample experiment?

b. We must know the population mean under some condition of the independent variable other than the one being tested.

When is a one-tailed test used?

b. When a relationship is predicted and the direction in which the scores will change is predicted

When statisticians report that the results from an experiment are significant, this means the results a. are scientifically important. b. are too unlikely to accept as sampling error. c. differ from what was predicted by the experimental hypotheses. d. do not differ from what was predicted by the null hypothesis.

b. are too unlikely to accept as sampling error.

Which of the following represents a Type I error? We say that something a. works when it really does. c. doesn't work when it really does. b. works when it really doesn't. d. doesn't work when it really doesn't.

b. works when it really doesn't.

Suppose you conduct an experiment and your is statistically significant at +3.45. How would you correctly interpret this result? a. c. b. d.

c.

The population mean for the Elementary Tenacity Test (ETT) is 150, with . A recent study of elementary school children participating in a school lunch program obtained the following ETT scores. Use a two-tailed z-test and . 145 180 176 152 148 142 179 163 159 154 167 172 146 169 157 150 161 160 153 165 a. Fail to reject . b. Reject and accept . c. Fail to reject . d. Reject and accept .

c.

Which of the following statements is true when is not rejected? a. The experiment worked. b. The data reflect a relationship found in nature. c. The data do not provide sufficient evidence of a relationship in nature. d. The data prove that the manipulation did not work.

c. The data do not provide sufficient evidence of a relationship in nature.

Which of the following is correct regarding alternative hypotheses?

c. They describe the population parameters represented by the sample data if the predicted relationship exists.

Which of the following is correct regarding experimental hypotheses?

c. They describe the predicted relationship we may or may not find in an experiment.

Suppose you have randomly selected high school students to take a course to improve their SAT scores. You find that the mean of their subsequent SAT scores is not significantly different from the population mean of SAT scores for those students who have not taken the course. Which of the following statements is the most appropriate conclusion? a. We have proven that the course does not affect SAT scores. b. We have obtained evidence consistent with the notion that the course has an effect on SAT scores. c. We have obtained no convincing evidence that the course affects SAT scores. d. The evidence suggests that the course may have an effect on SAT scores.

c. We have obtained no convincing evidence that the course affects SAT scores.

When can the z-test be used in statistical hypothesis testing? a. When the measure of central tendency used for the raw scores is the median b. When the raw scores are transformed from a nominal scale to a ratio scale c. When the raw score population's standard deviation is known d. When the z-test standard deviation is known

c. When the raw score population's standard deviation is known

The power of a statistical test is the probability of a. failing to reject a false . c. rejecting a false . b. failing to reject a true . d. rejecting a true .

c. rejecting a false .

For a two-tailed test where = 0.05, is always equal to a. 1.96. c. ±1.96. b. +1.96. d. ±1.645.

c. ±1.96.

Suppose that a population is known to have a mean of 80. If a researcher predicts the experimental treatment will produce an increase in the population mean, then the null hypothesis for this statistical hypothesis test would state a. µ > 80 c. µ 80 b. µ 80 d. µ < 80

c. µ 80

Suppose you conduct an experiment and the is statistically nonsignificant at 0.65. How would you correctly interpret this result? a. c. b. d.

d.

If and what is the value of ? a. 2.58 c. -2.58 b. 0.52 d. 0.78

d. 0.78

If and what is the value of ? a. 0.20 c. 0.60 b. 5.00 d. 1.00

d. 1.00

Which of the following accurately defines a Type II error? a. Rejecting when it is true c. Failing to reject when it is true b. Rejecting when it is false d. Failing to reject when it is false

d. Failing to reject when it is false

Which of the following describe(s) the situation if the relationship you are testing in your experiment really exists?

d. The alternative hypothesis

When is a two-tailed test used?

d. When a relationship is predicted without stating the direction in which the scores will change

In a one-tailed test is significant only if it lies a. nearer than and has a different sign from . b. in the tail of the distribution beyond and has a different sign from . c. nearer than and has the same sign as . d. in the tail of the distribution beyond and has the same sign as .

d. in the tail of the distribution beyond and has the same sign as .

When experimental results are significant, this means that the ______ hypothesis has been ______. a. experimental; rejected c. null; accepted b. alternative; rejected d. null; rejected

d. null; rejected

The null hypothesis describes the

d. population parameters represented by the sample data if the predicted relationship does not exist.

If a sample mean is different from a particular population µ, we can conclude that the sample mean probably represents some other population or that

d. the sample mean occurred as a result of sampling error.