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Chapter 8: Q 33 (page 478)

The 95% confidence interval is:__________________.

Short Answer

Expert verified

The 95% confidence interval is [24.52,36.28]

Step by step solution

01

Given Information

The sample mean is 30.4minutes, that is, x炉=30.4

The random sample of 25 winter students was selected, that is, n=25

The population standard deviation is 15, that is, 蟽=15

we have to find the 95% confidence interval

02

Calculation 1

Now calculate the confidence interval using TI83 calculator using the steps given below,

Step 1: Press STAT and use the arrow (?) to TESTS.

Step 2: Now press the arrow ( 鈫�)to 7 : ZInterval and press enter.

Step 3: Then use the arrow (鈫�)to STATS and press enter.

03

Step  3 Calculation 2

Step 4: Now press the arrow (?) and enter the inputs as shown below,

04

Calculation 3

Step 5: Then press the arrow (?) to calculator and press enter. The output is given below,

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Most popular questions from this chapter

If it were later determined that it was important to be more than 90% confident and a new survey was commissioned, how would it affect the minimum number you need to survey? Why?

A telephone poll of 1000adult Americans was reported in an issue of Time Magazine. Another question in the poll was 鈥淸How much are] you worried about the quality of education in our schools?鈥� Sixty-three percent responded 鈥渁 lot鈥�. We are interested in the population proportion of adult Americans who are worried a lot about the quality of education in our schools.

a. Define the random variables Xand P鈥�in words.

b. Which distribution should you use for this problem? Explain your choice.

c. Construct a 95%confidence interval for the population proportion of adult Americans who are worried a lot about the quality of education in our schools.

i. State the confidence interval.

ii. Sketch the graph.

iii. Calculate the error bound.

d. The sampling error given by Yankelevich Partners, Inc. (which conducted the poll) is 卤3%. In one to three complete sentences, explain what the 卤3% represents.

If the Census wants to increase its level of confidence and keep the error bound the same by taking another survey, what changes should it make?

If the Census did another survey, kept the error bound the same, and surveyed only 50 people instead of 200, what would happen to the level of confidence? Why?

Suppose that the insurance companies did do a survey. They randomly surveyed 400drivers and found that 320claimed they always buckle up. We are interested in the population proportion of drivers who claim they always buckle up.

a. i. x = __________ ii. n = __________ iii. p鈥� = __________

b. Define the random variables Xand P', in words.

c. Which distribution should you use for this problem? Explain your choice.

d. Construct a 95%confidence interval for the population proportion who claim they always buckle up. i. State the confidence interval. ii. Sketch the graph. iii. Calculate the error bound.

e. If this survey were done by telephone, list three difficulties the companies might have in obtaining random results.
See all solutions

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