Project #36559 - self check

A researcher is going to perform a significance test for the difference between two population proportions (H0 : p1 = p2) based on the following sample statistics:X1 = 12,n1 = 20,X2 = 15,n2 = 30. Which of the following would be used to compute the value of z for this test?

 
The n's are too small to justify the use of z-procedures in this situation.
 
2. 

A random sample of 384 people in Dalto City, a mid-sized city, revealed 112 individuals who work at more than one job. A second random sample of 432 workers from East Dettweiler, another mid-sized city, found 91 people who work at more than one job. To conduct a significance test for a difference in the proportions of workers in Dalto City and East Dettweiler who work at more than one job, what's the pooled value for p̂, and what's the pooled standard error of the difference between the two sample proportions, respectively?

 
.5, .0303
.249, .017
.249, .0009
.251, .0303
.249, .0303
 
3. 

Consider the following data collected in two recent surveys of whether voters in cities A and B favor a ballot proposition in the next election.

City Sample Size In Favor
A 615 463
B 585 403


Suppose you're going to conduct a significance test to see if there's a difference between the two population proportions. What's the standard error of the estimate?
 
 
4. 

A random sample of 250 men yielded 175 who said they'd ridden a motorcycle at some time in their lives, while a similar sample of 215 women yielded only 43 that had done so. Find a 99% confidence interval for the difference between the proportions of men and women who have ridden motorcycles.

 
.5 ± .078
.5 ± .103
.5 ± .085
.4688 ± .085
.5 ± .112

 

 

5. Over the years grades in an introductory statistics course were recorded and showed the following proportions:

A = 0.20 B = 0.30 C = 0.30 D = 0.10 and F = 0.10

This year there were 200 students in the introductory statistics class and they received the following grades

A = 56 B = 74 C = 60 D = 9 and F =1

We are interested in knowing if the distribution of grades this year is the same as in the past. The plan is to use a X2 statistic. The X2 statistic has appromimately a chi-square distribution. How many degrees of freedom does this distribution have?

 
4
5
200
199

 
6. 

Over the years grades in an introductory statistics course were recorded and showed the following proportions:

A = 0.20 B = 0.30 C = 0.30 D = 0.10 and F = 0.10

This year there were 200 students in the introductory statistics class and they received the following grades

A = 56 B = 74 C = 60 D = 9 and F =1

To test whether the distribution of grades this year is the same as in the past the X2 statistic is calculated. The component of this X2 statistic corresponding to a grade of C is

 
(O-E)2/E = 11,880.3
(O-E)2/E = 30
(O-E)2/E = 1
(O-E)2/E = 0
 
7. 

Over the years grades in an introductory statistics course were recorded and showed the following proportions:

A = 0.20 B = 0.30 C = 0.30 D = 0.10 and F = 0.10

This year there were 200 students in the introductory statistics class and they received the following grades

A = 56 B = 74 C = 60 D = 9 and F =1

We are interested in knowing if the distribution of grades this year is the same as in the past. The plan is to use a X2 statistic. The X2 statistic has a computed value of 33.77. The p-value of the test is

 
between 0.10 and 0.05
greater than 0.10
less than 0.01
between 0.05 and 0.01
 
8.

Over the years grades in an introductory statistics course were recorded and showed the following proportions:

A = 0.20 B = 0.30 C = 0.30 D = 0.10 and F = 0.10

This year there were 200 students in the introductory statistics class and they received the following grades

A = 56 B = 74 C = 60 D = 9 and F =1

We are interested in knowing if the distribution of grades this year is the same as in the past. The plan is to use a X2 statistic. We may assume the X2 statistic has an approximate chi-square distribution because of the following?

 
We may not assume the X2 statistic has an approximate chi-square distribution because there is only one person in the F grade category.
The number of categories is small relative to the number of observations.
The expected number of people in each grade category is greater than 5.
The sample size is 200, which is large enough for the chi-square approximation to be valid.
 
9. 

Over the years grades in an introductory statistics course were recorded and showed the following proportions:

A = 0.20 B = 0.30 C = 0.30 D = 0.10 and F = 0.10

This year there were 200 students in the introductory statistics class and they received the following grades

A = 56 B = 74 C = 60 D = 9 and F =1

To test whether the distribution of grades this year is the same as in the past the X2 statistic is calculated. The grade category that contributes the largest component to the X2 statistic is

 
A
C
B
F
D

 

10. The following data were obtained from a company which manufactures special plastic containers which are to hold a specified volume of hazardous material. On each of the three 8 hour shifts workers are able to make 500 of the containers. Some containers do not meet specifications as required by the company's customer because they are too small, others because they are too large. If conformance to specifications is independent of shift, the expected number of containers that meet specification on the 4pm shift is:


Conformance to Specification

Shift Too small Within Spec. Too Large
8 am 36 452 12
4 pm 24 443 33
midnight 12 438 50

If conformance to specifications is independent of shift, the expected number of containers that meet specification on the 4 pm shift is:

 

 
452
166.67
444
31.67
444.33
 
11. 

Are all employees equally prone to having accidents? To investigate this hypothesis, Parry (1985) looked at a light manufacturing plant and classified the accidents by type and by age of the employee.

Accident Type

Age Sprain Burn Cut
Under 25 9 17 5
25 or over 61 13 12

A chi-square test gave a test-statistic of 20.78. If we test at alpha = .05:

 

 
Age seems to be independent of accident type.
There appears to be a 20.78% correlation between accident type and age.
Accident type does not seem to be independent of age.
The proportion of sprain, cuts and burns seems to be similar for both age classes.
There appears to be no association between accident type and age.
 
12. 

A random sample of 100 members of a union are asked to respond to two questions: Question 1. Are you happy with your financial situation? Question 2. Do you approve of the Federal government's economic policies? The responses are:

Question 1

    Yes No Total
Question 2 Yes 22 48 70
  No 12 18 30
  Total 34 66 100

To test the null hypothesis that response to Question 1 is independent of response to Question 2 at 5% level, the expected frequency for the cell (Yes,Yes) and the critical value of the associated test statistic are:

 
23.8 and 7.81 respectively
23.8 and 1.96 respectively
10.2 and 7.81 respectively
10.2 and 3.84 respectively
23.8 and 3.84 respectively
 
13. 

Doctors' practices have been categorized as to being Urban, Rural, or Intermediate. The number of doctors who prescribed tetracycline to at least one patient under the age of 8 were recorded for each of these practice areas. The results are:

 

  Urban Intermediate Rural
Tetracycline 95 74 31
No tetracycline 126 84 30

If the county type of practice and the use of tetracycline are independent, then the expected number of rural doctors who prescribe tetracycline is:

 
27.7
62
31.0
1.37
51
 
14. 

Doctors' practices have been categorized as to being Urban, Rural, or Intermediate. The number of doctors who prescribed tetracycline to at least one patient under the age of 8 were recorded for each of these practice areas. The results are:

 

  Urban Intermediate Rural
Tetracycline 95 74 31
No tetracycline 126 84 30

The critical value (table value) of the test statistic when the level of significance alpha =0.05, is:

 
7.38
1.37
7.81
5.99
12.59

Subject Mathematics
Due By (Pacific Time) 07/28/2014 03:00 pm
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