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Relaxing in the sauna Researchers followed a random sample of 2315middle-aged men from eastern Finland for up to 30years. They recorded how often each man went to a sauna and whether or not he suffered sudden cardiac death (SCD). The two-way table shows the data from the study.

a. State appropriate hypotheses for performing a chi-square test for independence in this setting.

b. Compute the expected counts assuming that H0is true.

c. Calculate the chi-square test statistic, df, and P-value.

d. What conclusion would you draw?

Short Answer

Expert verified

(a) The appropriate hypothesis is the null hypothesis.

(b) The expected count is,


1or FEWER2-3
4or MORE
YES49.33
124.18
16.50
NO551.67
1388.82
184.50

(c) The test statistics is 2=6.0323,df=2,P-value=0.025<P<0.05.

(d) There are many convincing pieces of evidence for the association between SCD and weekly sauna frequency.

Step by step solution

01

Part (a) Step 1: Given information

We need to find out the appropriate hypothesis for performing a chi-square test for independence in this setting.

02

Part (a) Step 2: Explanation

We know that

The null hypothesis asserts that the variables are unrelated, whereas the alternative hypothesis asserts that they are.

H0is there is no association between SCD and Weekly sauna frequency.

H is there is an association between SCD and Weekly sauna frequency.

03

Part (b) Step 1: Given information

We need to find the expected counts.

04

Part (b) Step 2: Explanation

From part (a)

We know that

Expected frequencies are a product of row and column total divided by table total. So,

ROW AND COLUMN NUMBER
EXPECTED FREQUENCY
E1149.33
E12
124.18
E13
16.50
E21
551.67
E22
1388.82
E23
184.50
05

Part (c) Step 1: Given information

We need to find the test statistics, df, P-value.

06

Part (c) Step 2: Explanation

From parts (a) and (b)

We know that

The squared differences between the actual and predicted frequencies, divided by the expected frequency, make up the chi-square subtotals.

Therefore, test-statistics is,2=6.0323

And

df=2P-value=0.025<P<0.05=0.048989

07

Part (d) Step 1: Given information

We need to find out the conclusion drawn.

08

Part (d) Step 2: Explanation

From the parts (a) ,(b) and (c)

We know that

There are many convincing pieces of evidence for the association between SCD and weekly sauna frequency.

And this is the conclusion we drew.

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Most popular questions from this chapter

The two-way table shows the results of the experiment described in

Exercise 28.

Hatching Statuswater temperature:coldwater temperature:neutral
water temperature:hot
Total
Yes16
38
75
129
No11
18
29
58
Total
27
56
104
187

a. State the appropriate null and alternative hypotheses.

b. Show the calculation for the expected count in the Cold/Yes cell. Then provide a

complete table of expected counts.

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d. (1825)2100+(2225)2100+(3925)2100+(2125)2100

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A random sample of traffic tickets given to motorists in a large city is examined. The tickets are classified according to the race or ethnicity of the driver. The results are summarized in the following table.

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We wish to test H0: The racial/ethnic distribution of traffic tickets in the city is the same as the racial/ethnic distribution of the city's population.

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a. Should we use a chi-square test for homogeneity or a chi-square test for independence in this setting? Justify your answer.

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Roulette Refer to Exercise 2.

a. Confirm that the expected counts are large enough to use a chi-square distribution to calculate the P-value. What degrees of freedom should you use?

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