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Statistics, Sample Test (Exam Review)
Module 4: Chapter 8 Review
Chapter 8 : Hypothesis Testing
Chapter 8 : Hypothesis Testing
1. Answer the following:
a. A test of hypothesis is always about a population ______________
b. The observed value of a test statistic is the value ________ for a sample
statistic.
c. As the sample size gets larger, both type I and type II errors decrease or
increase?
d. Define type I error.
e. Define type II error.
f. The value of  is called the ______________
g. The value of  is called the ______________
h. The value of 1 
− is called the ______________
2. In 1990, 5.8% of job applicants who were tested for drugs failed the test. At the 0.01
significance level, test the claim that the failure rate is now lower if a simple random
sample of 1520 current job applicants result in 58 failures. Does the result suggest
that fewer job applicants now use drugs?
a) State the null and alternative hypothesis.
b) Calculate the value of test statistic.
c) Find the critical value.
d) Make a decision.
e) Find the p-value & make a decision. Is this decision in agreement with the
previous one?
f) What is type I error, what is the probability of making type I error.
3. A sample of 54 bears has a mean weight of 182.9 lb. Let’s assume that the standard
deviation of weights of all such bears is known to be 121.8 lb, at 0.1
 = , is there
enough evidence to support the claim that the population mean of all such bear
weights is less than 200 lb?
a. State the null and alternative hypothesis.
b. Calculate the value of test statistic.
c. Find the critical value(s).
d. Make a decision.
4. Sixteen new textbooks in the college bookstore, had prices with a mean of $70.41 and
a standard deviation of $19.70. Use a 0.05 significance level to test the claim that the
mean price of a textbook at this college is less than $75? Assume normal population.

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5. Tests in the author's past statistics classes have scores with a standard deviation equal
to 14.1. One of his current classes now has 27 test scores with a standard deviation of
9.3. Use a 0.01 significance level to test the claim that this current class has less
variation than past classes. Does a lower standard deviation suggest that the current
class is doing better? Assume the population is normal.
6. Consider a population of frogs living on an island. We believe that the
frogs may be members of a species called Rana Pipiens. The mean length
of Rana Pipiens is known to be 11cm.
The following length values (cm) were obtained for a sample of
individuals from the island:
10.6 11.2 10.6 9.9 10.7 9.8 10.1 9.6 12.5 11.2 10.3
10.1 8.9 11.1 9.3 11.9 9.7 11.5 10.3 11.2
Do these frogs have sizes that are consistent with them being Rana
Pipiens or not? Are these frogs Rana Pipiens or not? Use a 0.05
significance level.