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R8.4. We love football! A recent Gallup Poll conducted telephone interviews with a random sample of adults aged 18 and older. Data were obtained for 1000 people. Of these, 37% said that football is their favorite sport to watch
on television.
(a) Define the parameter pin this setting. Explain to someone who knows no statistics why we can鈥檛 just say that 37%of all adults would say that football is their favorite sport to watch on television.
(b) Check conditions for constructing a confidence interval for p.
(c) Construct a 95% confidence interval for p.
(d) Interpret the interval in context.

Short Answer

Expert verified

(a) The population proportion pindicates the percentage of adults aged 18and up who consider football to be their favorite sport.

(b) All the parameters satisfied.

(c) The confidence interval is (0.341,0.3999).

(d) A 95% confident that the true population proportion of adults who say that football is their favorite sport to watch on television is between 0.3401 and0.3999.

Step by step solution

01

Part (a) Step 1: Given information

To define the parameter p in this setting. Then to explain who knows no statistics why we can鈥檛 just say that 37% of all adults would say that football is their favorite sport to watch on television.

02

Part (a) Step 2: Explanation

Let, the number of trials is (n)=1000.
The sample proportion is (p^)=0.37.
The confidence interval is calculated as follows:
p^-za/2p^(1-p^)n<p<p^+za/2p^(1-p^)n
The population proportion p indicates the percentage of adults aged 18 and up who consider football to be their favorite sport.

03

Part (b) Step 1: Given information

To check conditions for constructing a confidence interval for p.

04

Part (b) Step 2: Explanation

The following requirements are met:
(1) The sample was chosen at random.
(2) The total number of successes and failures exceeds 10.

(3) The sample size is 10% less than the population size.
As a result, all of the parameters have been met.

05

Part (c) Step 1: Given information

To construct a 95%confidence interval for p.

06

Part (c) Step 2: Explanation

Using a Ti-83 calculator, the following confidence interval was calculated:

As a result, the confidence interval is (0.341,0.3999).

07

Part (d) Step 1: Given information

To interpret the interval in context.

08

Part (d) Step 2: Explanation

Let, p^=37%

=0.37

Then,

n=1000

Using table IIfor confidence level 95%,

z/2=1.96

Determine the margin of error as:

E=z/2p^(1-p^)n

=1.960.37(1-0.37)1000

0.0299

09

Part (d) Step 3: Explanation

Determine the confidence interval as:
0.3401=0.37-0.0299

=p^-E<p<p^+E

=0.37+0.0299

=0.3999

Asa result, 95%confident that the true population proportion of adults who say that football is their favorite sport to watch on television is between 0.3401and 0.3999.

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