STAT TEST

Dear Students,

This is our 7th and the last week of our course. I know you have worked hard to grasp the new topics in biostatistics. Congratulations! I truly appreciate your sincere efforts.

I also tried my best to make the things easier for you.

Please read my notes on this week's topic, nonparametric test. In reading, once you get out of the loop, please go back and read again, if needed go to the textbook chapter. Go slowly and steadily. Please don't give up. I will try to understand your efforts and reward you with grading.

If you have any questions, please don't hesitate to ask me in advance.

Thank you for bearing with me throughout the course.

Please take the test.

Good luck!

Question at position 1

1

True or False

1 point

Question at position 1

A statistical method in which data are not required to fit a normal distribution is called nonparametric statistics.

A statistical method in which data are not required to fit a normal distribution is called nonparametric statistics.

True

False

Question at position 2

2

True or False

1 point

Question at position 2

We use nonparametric tests when the sample size is large.

We use nonparametric tests when the sample size is large.

True

False

Question at position 3

3

True or False

1 point

Question at position 3

In general, nonparametric tests deal with ordinal data.

In general, nonparametric tests deal with ordinal data.

True

False

Question at position 4

4

True or False

1 point

Question at position 4

In nonparametric tests, variables are ranked from highest to lowest.

In nonparametric tests, variables are ranked from highest to lowest.

True

False

Question at position 5

5

True or False

1 point

Question at position 5

It is essential to check that the sum of ranks is always equal to n (n+1)/2.

It is essential to check that the sum of ranks is always equal to n (n+1)/2.

True

False

Question at position 6

6

True or False

1 point

Question at position 6

Smaller values of U test support research hypothesis (H1) and larger values of U test support the null hypothesis (H0).

Smaller values of U test support research hypothesis (H1) and larger values of U test support the null hypothesis (H0).

True

False

Question at position 7

7

Multiple Answer

3 points

Question at position 7

What are the assumptions of parametric tests?

What are the assumptions of parametric tests?

Normality

Independence

Equal variance

Presence of extreme outliers.

Question at position 8

8

Essay

26 points

Question at position 8

A small study (n=11) is designed to assess whether there is an association between smoking during pregnancy and antepartum hemorrhage. Antepartum hemorrhages are genital bleeding during pregnancy after the 28th week of pregnancy up to the delivery. The following data represent the antepartum hemorrhage in women from 11 clinics who reported smoking in pregnancy and who did not.

Number of women who smoked in pregnancy: 5 0 3 2 7 6 (n1 = 6)

Number of women who did not smoked in pregnancy: 1 4 8 5 9 (n2 = 5)

Answer the following questions:

1. Sample size (n)? (1 point)

2. Rewrite the data in ordered forms (from smallest to largest). (2 points)

3. Rank the data from smallest to largest) (2 points)

4. Sum ranks for smokers' group. (3.5 points)

5. Sum ranks for nonsmokers' group. (3.5 points)

6. Prove that n (n+1)/2 = Total sum of ranks. (3 points)

7. Is there any evidence of a difference in antepartum bleeding between the smokers and nonsmokers groups. Show all 5 steps of hypothesis testing as follows:

Step 1; Set up hypotheses and determine the level of significance (1 points);

Step 2: Select appropriate test statistic (Hints: Since we have two independent sample, so use Mann-Whitney-U test) (2 points);

Step 3: Set up the decision rule (Hints: Find the critical value in Table 5 in textbook and decide when we will reject the null) (3 points);

Step 4: Compute the test statistic using the formula for U1 and U2 (See the formula for U1 and U2; (3 points); and

Step 5: Conclude your final decision to accept or to reject the null with your explanation of what does it mean.(2 points).