propability

23 May propability

1 The probability that a person likes to watch Football given that she also likes to watch basketball?

	Football	No Football
Basketball	22	11
No basketball	38	29

2 How many different simple random samples of size 4 can be obtained from a population whose size is 44?

3 Find the sample mean as indicated in the sample : 24,17,6,13,10

4 Determine the critical values for this test of a population standard deviation. A two-tailed test for a sample of size n=23 at the a=0.1 level of significance.

 

5 An agricultural researcher is interested in estimating the mean length of the growing season in a region. Treating the last 10 years as a simple random sample, he obtains the following data, which represent the number of days of the growing season.

156, 162, 150, 143, 163, 184, 190, 178, 164, 151

6 One year Frank had the lowest ERA (earned-run average, mean number of runs yielded per nine innings pitched) of any male pitcher at his school, with an ERA of 2.58.  Also, Susan had the lowest ERA of any female pitcher at her school with an ERA of 2.74. for the males the mean ERA was 4.9991 and the standard deviation was 0.885 for the females the mean ERA was 4.287 and the standard deviation was 0.748. Find their respective z-scores. Which player had the better year relative to their peers, Frank or Susan? (Note: in general, the lower ERA, the better pitcher).

Frank had an ERA with a z-score of

A.        Susan had a better year because of a lower z-score.

B.        Frank had a better year because of a lower z-score.

C.        Frank had a better year because of a higher z-score.

D.        Susan had a better year because of a higher z-score.

 

7 Determine the critical value for a right-tailed test regarding a population proportion at the a=0.05 level of significance.

8 For the following data set compute the correlation coefficient.

X         1          4          7          7          9

Y         1.2       1.5       1.9       2.0       2.6

 

9 For the data set below determine the least –squares regression line

X         30        40        50        60        70

Y         71        69        71        48        44

10 Suppose a professor records the number of days absent and the final grade for the students in his class. Use the data in the table below to answer questions a through c.

Number of absent x	0	1	2	3	4
Final grade	82.3	85.9	77.5	80	77.6

 

 

The slope indicates the ratio between the average final grade and the average number of absences.

The slope indicates average final grade.

The slope indicates the average number of absences.

It is not appropriate to interpret the slope because it is not equal to 0.

 

The y-intercept indicates the average final grade for the population.

The y-intercept indicates the average number of absences for the population.

The y-intercept indicates the final grade of the student with the most absences.

The y-intercept the average final grade for a student with no absences.

It is not appropriate to interpret the y-intercept because it is outside the scope of the model.

 

C. Predict the final grade for a student who misses two class periods.

The predicted final grade is __________.

11. Determine the critical values for this test of a population standard deviation. A two-tailed test for a sample of size n=23 at the  a=0.1 level of significance. Use the Chi-square distribution.

The critical values for the two-tailed test is _____________>

12According to an airline, flights on a certain route are on time 75% of the time. Suppose 13 flights are randomly selected and the number of on time flights is recorded.

Exactly 11 flights are on time

At least 11 flights are on time

Between 10 and 12 inclusive