Practice test 4A Hypothesis testing

1. 1
Statistics Practice Test 4A (Part One)
Hypothesis Testing
1. A test of hypothesis is always about a population ______________
2. The observed value of a test statistic is the value ________ for a sample statistic.
3. As the sample size gets larger, both type I and type II errors decrease or increase?
4. Define type I error.
5. Define type II error.
6. The value of  is called the ______________
7. The value of  is called the ______________
8. The value of 1  is called the ______________
9. 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 results 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.
10. 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.
11. 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?
12. 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.