What is the Alternative hypothesis? What is the critical value? What is the expe

Question

What is the Alternative hypothesis?

What is the critical value?

What is the expected value of those with a present diagnosis of gonorrhea having a previous episode of urethritis?

What is the expected value of those with a present diagnosis of gonorrhea not having a previous episode of urethritis?

What is the expected value of those with a present diagnosis of nongonococcal urethritis having a previous episode of urethritis?

What is the expected value of those with a present diagnosis of nongonococcal urethritis not having a previous episode of urethritis?

What is the test statistic?

is there an association between present diagnosis and prior episodes of urethritis?

Use the following information to answer questions 11-18. Suppose researchers do an epidemiologic investigation of people entering a sexually transmitted disease clinic. Given the observed table below and a 30.05, conduct a chi-square test for association to determine if there is an association between present diagnosis and prior episodes of urethritis. Previous Episodes of Urethritis No Yes 40 160 Present Gonorrhea 105 Diagnosis Nongonococcal Urethritis 50 10. What is the alternative hypothesis? a. There is no association between present diagnosis and prior episodes of urethritis b. There is an association between present diagnosis and prior episodes of urethritis c. The presence of diagnosis is greater for those with a prior episodes of urethritis d. The presence of diagnosis is less for those with a prior episodes of urethritis 11. What is the critical value? b, 3.84 c. 5.02 d. 6,63

Explanation / Answer

Null hypothesis: H0: There is no association between present diagnoisis and prior episodeof urethritis

Alternative Hypothesis: H1: There is association between present diagnoisis and prior episodeof urethritis

The observed frequencies are

The expected value of those with a present diagnosis of gonorrhea having a previous episode of urethritis is

(200*210) / 355 = 118.31

The expected value of those with a present diagnosis of gonorrhea not having a previous episode of urethritis is

(200*145) / 355 = 81.69

The expected value of those with a present diagnosis of nongonococcal urethritis having a previous episode of urethritis is (155*210)/ 355= 91.69

The expected value of those with a present diagnosis of nongonococcal urethritis not having a previous episode of urethritis is (145*210)/ 355= 63.31

The chisquare contributions are

Degrees of freedom: 1

Test Statistic, X^2: 82.37
Critical X^2: 3.841456
P-Value: 0.0000

Here P-value < alpha 0.05, we reject H0

Thus we conclude that There is association between present diagnoisis and prior episodeof urethritis

Yes No Total Gonorrhea 160 40 200 Urethritis 50 105 155 Total 210 145 355

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