True /False
1. __True___ The selection of
H o and H a depend on the objectives of the study.
2.__False___ If the null hypothesis is not rejected, then there is strong statistical evidence that the null hypothesis is not true.
3.__ False ___ The fundamental idea behind hypothesis testing is to reject the null hypothesis only when the observed sample is very
likely to have occurred when H o is true.
4.__ False ___ The decision to reject or fail to reject
H o is based on the value of the sample variance.
5.__ True ___Large p-values indicate that the observed sample is consistent with the null hypothesis.
6.__ True ___It is customary to say that the result of a hypothesis test is statistically significant when the p-value is smaller than
.
7.___ False __ In a large sample (n > 30) z test for a population proportion, the calculated value of z expresses a probability.
8.__ True ___ For testing
H o :   50 versus H a  50 , a calculated value of z  1.98 will have a smaller P-value than
z  1.8 .
9___ False ___In an experiment involving two treatments, rejection of H o : 1   2  0 in favor of H a : 1   2  0 suggests that
treatment 1 caused the larger values of the variable to occur.
10.__ False ___ A t test for 1   2 should be used only when the sample sizes are more than thirty.
For questions #11 through #16, use the following list of possible answers. Answers may be used more than once.
Each correct answer is worth three points.
5)
H o :   o
H A :   o
9)
H A : 1   2
1)
2)
6)
10)
H A :   o
H A :   o
H o : 1   2
7)
H A :   o
H o :   o
11)
H A : 1   2
3)
4)
H o : 1   2
8)
H A : 1   2
12)
H A : 1   2
DO NOT PERFORM ANY TESTS FOR #11 THROUGH #16.
__1____11. An insurance agent is interested in the amount of money paid out in claims involving fire damage. A sample of 20
claims was selected. The average pay-out was claimed to be $2700. What is the null hypothesis?
__2_____12. Cyanide concentrations in the Netherlands are supposed to be less than 80 kg/mg. Environmental Science & Technology
(Oct. 1993) reported on a study of contaminate soil in The Netherlands. Seventy-two 400-gram soil specimens were sampled, dried,
and analyzed for the contaminant cyanide. The cyanide concentration [in milligrams per kilogram (mg/kg) of soil] of each soil
specimen was determined using an infrared microscopic method. The sample resulted in a mean cyanide level of x = 84mg/kg and a
standard deviation of s = 2.5 mg/kg. What is the alternative hypothesis?
___5____13. A light bulb manufacturer (Brand 1) claims to have a light bulb that lasts 500 hours longer than its competitor, Brand 2.
A study is made using one hundred light bulbs of Brand 1. The average life span of Brand 2 is known. What is the alternative
hypothesis?
__12_____14. Two surveys are done at the same time. One is given to men (group 1), and the other is given to women (group 2). It is
claimed that the percentage of men completing the survey is higher than the percentage of women. What is the alternative hypothesis?
2 or 5_______15. A diet plan claims to allow a person to lose fifteen pounds in two weeks. The weight of twenty- five individuals is
recorded. After two weeks, the weights are recorded again. What is the alternative hypothesis? Before - After
__8_____16. A group of fifty students (Group 1) volunteer to take an ACT preparation course that claims to improve test scores. A
group of seventy students (Group 2) take the ACT without having taken the preparation course. The scores from each group are
recorded. What is the alternative hypothesis?