Question 8

What does the central limit theorem tell us about the mean of a large sample?

Ifthe population is skewed, then for more than 10 sample size the sampling distribution of sample mean will be normal.

Ifthe population is not symmetric, then for more than 20 sample size the sampling distribution of sample mean will be normal

Ifthe population is normal distribution, then for any sample size the sampling distribution of sample mean will be normal.

At least 30 samples are randomly collected.

Question 9

What do we call the statement that determines if the null hypothesis is rejected?

Alternate hypothesis

Test statistic

Critical value

Decision rule

Question 10

How many recent LU graduates should be interviewed if the university wishes to estimate the mean salary of students coming out of their programs? Assume the estimate is to be accurate within 2 thousand dollars, 19 times out of 20, and that previous studies of recent graduates have found a standard deviation of 10 thousand dollars.

97

95

96

98

Question 11

A confidence interval for a population mean

estimates a likelihood or probability

estimates the population range

estimates a likely interval for a population mean

estimates the population standard deviation

Question 12

Suppose a researcher, interested in obtaining an estimate of the average level of some enzyme in a certain human population, takes a sample of 95 individuals, and computes a sample mean of 19.

The variable of interest is approximately normally distributed with a standard deviation of 5.63.What is a reasonable range of values for the population mean at a 90% level of confidence?

(18.05, 19.95)

(19.95, 18.05)

(17.9, 20.1)

(20.68, 23.32)

(19, 19.05)

Question 13

i. Two examples of a hypothesis are: 1) mean monthly income from all sources for senior citizens is $841 and 2) twenty percent of juvenile offenders ultimately are caught and sentenced to prison.

ii. Hypothesis testing is a procedure based on sample evidence and probability theory to decide whether the hypothesis is a reasonable statement.

iii. We call a statement about the value of a population parameter a hypothesis.

(i) and (iii) are correct statements but not (ii).

(i) is a correct statement but not (ii) or (iii).

(i), (ii), and (iii) are all correct statements.

(i), (ii), and (iii) are all false statements.

Question 14

The Pew Internet and American Life Project reported findings from a study in 2003 that 18 percent of Internet users have used it to search for information regarding experimental treatments or medicines. The sample consisted of 1220 adult Internet users, and information was collected from telephone interviews. We wish to construct a 95 percent confidence interval for the proportion of Internet users in the sampled population who have searched for information on experimental treatments or medicines.

Please give the brief calculation process to show the confidence interval.

Question 15

It is claimed that in a bushel of peaches less than ten percent are defective. A sample of 400 peaches is examined and 50 are found to be defective.

If a = 0.025, what will be the decision?

Reject the null and conclude the defects are not greater than 10%

Fail to reject the null and conclude the defects are not less than 10%

Reject the null and conclude the defects are greater than 10%

Fail to reject the null and conclude the defects are not greater than 10%