# 1.2 Skills practice exam 3: chapters 7, 8, 9, & 10  (Page 2/2)

The null hypothesis is“the percentage of men who score 45 points or more (out of 50 points) on a statistics test at De Anza College is the same as the percentage of women who score 45 points or more.”The alternate hypothesis is“the percentage of men who score 45 points or more (out of a 50 point test) on a statistics test at De Anza College is more than the percentage of women who score 45 points or more.”

The appropriate hypothesis test to perform and distribution to use is

• ## A

a test of two population proportions, independent groups; Student-t distribution
• ## B

a test of a single population proportion; Normal distribution
• ## C

a test of two population means, independent groups; Normal distribution
• ## D

a test of two population proportions, independent groups; Normal distribution

D

• ## B

t with degrees of freedom = 15
• ## C

t with degrees of freedom = 14
• ## D

Normal with standard deviation \$241.93

C

For problems 14 and 15: Buses on a particular route stop in front of De Anza College every 20 minutes between 3:00 p.m. and 1:00 a.m. The waiting times are equally likely. We asked the 33 people waiting at 6:45 p.m. how long they had been waiting, and then calculated the average wait time for those people.

The distribution of the average wait times is:

• ## A

N( 10 , 1. 0050 )

U( 0 , 20 )
• ## C

N( 10 , 5.7735)
• ## D

Exp ( 1 20 )

A

The probability that the average wait time is no more than 15 minutes is

1

0. 7500

0. 7769
• ## D

0

A

Which probability statement best describes the graph? The horizontal axis has the label Xbar.

P( Xbar>6 )

P( Xbar<3 )
• ## C

P( Xbar>6 or X<3 )
• ## D

P( 3<Xbar<6 )

D

Questions 17 and 18 refer to the following: A radio news story claimed that half of all U.S. adults have Internet access. In a national poll about Internet usage (The Pew Internet Project), 12,638 U.S. adults were surveyed and it was found that 6413 of those surveyed had Internet access. At a 5% level of significance, perform a hypothesis test to test the claim made by the radio news story.

The hypothesis test is:

• ## A

right - tailed
• ## B

left - tailed

two–tailed
• ## D

no-tailed

C

The correct conclusion is:

• ## A

The percentage of U.S. adults that have Internet access is not one-half.
• ## B

more than half of all U.S. adults have Internet access.
• ## C

half of all U.S. adults have Internet access.
• ## D

less than half of all U.S. adults have Internet access.

C

Questions 19 - 21 refer to the following: An organic fertilizer and a conventional chemical fertilizer are tested to determine if the organic fertilizer produces more blossoms per stalk. 43 pairs of seed (the pair of seeds come from the same parent plant) are treated. One seed is treated with the organic fertilizer and the other seed is treated with the conventional chemical fertilizer. After a growing season of identical watering and sunlight, the number of blossoms on each stalk in a matched pair is recorded. For each pair, the difference in the number of blossoms per stalk (organic fertilizer plant blossoms–conventional chemical fertilizer plant blossoms) is computed. _The statistics are: xd = 2.2 sd = 5.3 n = 43

What type of hypothesis test is conducted?

• ## A

Test of a single population mean
• ## B

Test of two population proportions, independent groups
• ## C

Matched or Paired Samples
• ## D

Test of two population means, independent groups

C

Select the appropriate alternate hypothesis.

µd£0

µd>0

µd>2.2
• ## D

µd£2.2

B

What is the correct conclusion?

• ## A

The organic fertilizer does result in more blossoms per stalk
• ## B

The organic fertilizer does not result in more blossoms per stalk.
• ## C

The organic fertilizer results in the same number of blossoms per stalk
• ## D

The conventional chemical fertilizer does result in more blossoms per stalk

A

Problems 22–24 refer to the following: Based on data from the 2000 Census the average age of a Baldwin County, Alabama resident is 39 years with a standard deviation of 22. 6 . The data is normally distributed.

The median age, in years, is:

39

22.6

19.5
• ## D.

There is not enough information.

A

If 100 residents are surveyed, the IQR for the average age is:

0. 30

30.5

3.04
• ## D.

There is not enough information.

C

Questions 24–25 refer to the following: Students doing a statistics project at Central City College found that the amount of time a teenager spends cleaning his/her room each week is exponentially distributed with a mean of 20 minutes.

What is the probability that 50 randomly selected teenagers spend, on average, between 15 and 30 minutes cleaning their rooms each week?

0.7500

0.2902

0.2492
• ## D

0.9612

D

Find the 70th percentile for the average amount of time 50 teenagers spend cleaning their rooms each week.

70

21.5

30.5
• ## D

7.1

B

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