
Concept explainers
The following four 2×2 tables, presented without labels or titles, provide simplified opportunities to practice your computational skills. Calculate chi square for each.
HINTS:
• Calculate the expected frequencies for each cell with Formula 10.2. Double check to make sure you are using the correct row and column marginals for each cell.
• It may he helpful to record the expected frequencies in table format—see Tables 10.4 and 10.8.
• Use a computational table to organize the calculation for Formula 10.1—see Tables 10.5 and 10.9.
• Follow the step-by-step instructions.
• Double-check to make sure you are using the correct values for each cell.
a. | 20 | 25 | 45 | c. | 25 | 15 | 40 |
2545 | 2045 | 4590 | 3055 | 3045 | 60100 | ||
b. | 10 | 15 | 25 | d. | 20 | 45 | 65 |
2030 | 3045 | 5075 | 1535 | 2065 | 35100 |

(a)
To find:
The chi square value for the given information.
Answer to Problem 10.1P
Solution:
The chi square value is 1.12.
Explanation of Solution
Given:
The given table of information is,
a. | 20 | 25 | 45 |
25 | 20 | 45 | |
45 | 45 | 90 |
Description:
The confidence interval is an interval estimate from the statistics of the observed data that might contain the true value of the unknown population parameter.
Formula used:
For a chi square, the expected frequency fe is given as,
fe=Row marginal×Column marginalN
Where N is the total of frequencies.
The chi square statistic is given by,
χ2(obtained)=∑(fo−fe)2fe
Where fo is the observed frequency,
And fe is the expected frequency.
Calculation:
From the given information,
The row marginal is 45, the column marginal is 45 and N is 90.
The observed frequency is given as,
fe=Row marginal×Column marginalN
Substitute 45 for row marginal, 45 for column marginal and 90 for N in the above formula.
fe=45×4590=22.5
Consider the following table,
6.25 | fo | fe | fo−fe | (fo−fe)2 | (fo−fe)2/fe |
20 | 22.5 | −2.5 | 6.25 | 0.28 | |
25 | 22.5 | 2.5 | 6.25 | 0.28 | |
25 | 22.5 | 2.5 | 6.25 | 0.28 | |
20 | 22.5 | −2.5 | 6.25 | 0.28 | |
Total | 90 | 90 | 0 | χ2=1.12 |
The value fo−fe is obtained as,
Substitute 20 for fo and 22.5 for fe in the above formula.
fo−fe=20−22.5=−2.5
Squaring the above obtained result,
(fo−fe)2=(−2.5)2=6.25
Divide the above obtained result by fe.
(fo−fe)2fe=6.2522.5=0.28
Proceed in a similar manner to obtain rest of the values of (fo−fe)2/fe and refer above table for the rest of the values of (fo−fe)2/fe.
The chi square value is given as,
χ2(obtained)=∑(fo−fe)2fe=0.28+0.28+0.28+0.28=1.12
Thus, the chi square value is 1.12.
Conclusion:
The chi square value is 1.12.

(b)
To find:
The chi square value for the given information.
Answer to Problem 10.1P
Solution:
The chi square value is 0.0.
Explanation of Solution
Given:
The given table of information is,
b. | 10 | 15 | 25 |
20 | 30 | 50 | |
30 | 45 | 75 |
Description:
The confidence interval is an interval estimate from the statistics of the observed data that might contain the true value of the unknown population parameter.
Formula used:
For a chi square, the expected frequency fe is given as,
fe=Row marginal×Column marginalN
Where N is the total of frequencies.
The chi square statistic is given by,
χ2(obtained)=∑(fo−fe)2fe
Where fo is the observed frequency,
And fe is the expected frequency.
Calculation:
From the given information,
The observed frequency is given as,
fe=Row marginal×Column marginalN……(1)
Substitute 25 for row marginal, 30 for column marginal and 75 for N in equation (1).
f1=25×3075=10
Substitute 25 for row marginal, 45 for column marginal and 75 for N in equation (1).
f1=25×4575=15
Substitute 50 for row marginal, 30 for column marginal and 75 for N in equation (1).
f1=50×3075=20
Substitute 50 for row marginal, 45 for column marginal and 75 for N in equation (1).
f1=50×4575=30
Consider the following table,
6.25 | fo | fe | fo−fe | (fo−fe)2 | (fo−fe)2/fe |
10 | 10 | 0 | 0 | 0 | |
15 | 15 | 0 | 0 | 0 | |
20 | 20 | 0 | 0 | 0 | |
30 | 30 | 0 | 0 | 0 | |
Total | 75 | 75 | 0 | 0 | χ2=0.0 |
The value fo−fe is obtained as,
Substitute 10 for fo and 10 for fe in the above formula.
fo−fe=10−10=0
Squaring the above obtained result,
(fo−fe)2=(0)2=0
Divide the above obtained result by fe.
(fo−fe)2fe=0
Proceed in a similar manner to obtain rest of the values of (fo−fe)2/fe and refer above table for the rest of the values of (fo−fe)2/fe.
The chi square value is given as,
χ2(obtained)=∑(fo−fe)2fe=0+0+0+0=0.0
Thus, the chi square value is 0.0.
Conclusion:
The chi square value is 0.0.

(c)
To find:
The chi square value for the given information.
Answer to Problem 10.1P
Solution:
The chi square value is 1.51.
Explanation of Solution
Given:
The given table of information is,
c. | 25 | 15 | 40 |
30 | 30 | 60 | |
55 | 45 | 100 |
Description:
The confidence interval is an interval estimate from the statistics of the observed data that might contain the true value of the unknown population parameter.
Formula used:
For a chi square, the expected frequency fe is given as,
fe=Row marginal×Column marginalN
Where N is the total of frequencies.
The chi square statistic is given by,
χ2(obtained)=∑(fo−fe)2fe
Where fo is the observed frequency,
And fe is the expected frequency.
Calculation:
From the given information,
The observed frequency is given as,
fe=Row marginal×Column marginalN……(1)
Substitute 40 for row marginal, 55 for column marginal and 100 for N in equation (1).
f1=40×55100=22
Substitute 40 for row marginal, 45 for column marginal and 100 for N in equation (1).
f1=40×45100=18
Substitute 60 for row marginal, 55 for column marginal and 100 for N in equation (1).
f1=60×55100=33
Substitute 60 for row marginal, 45 for column marginal and 100 for N in equation (1).
f1=60×45100=27
Consider the following table,
6.25 | fo | fe | fo−fe | (fo−fe)2 | (fo−fe)2/fe |
25 | 22 | 3 | 9 | 0.41 | |
15 | 18 | −3 | 9 | 0.50 | |
30 | 33 | −3 | 9 | 0.27 | |
30 | 27 | 3 | 9 | 0.33 | |
Total | 100 | 100 | 0 | χ2=1.51 |
The value fo−fe is obtained as,
Substitute 25 for fo and 22 for fe in the above formula.
fo−fe=25−22=3
Squaring the above obtained result,
(fo−fe)2=(3)2=9
Divide the above obtained result by fe.
(fo−fe)2fe=922=0.41
Proceed in a similar manner to obtain rest of the values of (fo−fe)2/fe and refer above table for the rest of the values of (fo−fe)2/fe.
The chi square value is given as,
χ2(obtained)=∑(fo−fe)2fe=0.41+0.50+0.27+0.33=1.51
Thus, the chi square value is 1.51.
Conclusion:
The chi square value is 1.51.

(d)
To find:
The chi square value for the given information.
Answer to Problem 10.1P
Solution:
The chi square value is 1.43.
Explanation of Solution
Given:
The given table of information is,
d. | 20 | 45 | 65 |
15 | 20 | 35 | |
35 | 65 | 100 |
Description:
The confidence interval is an interval estimate from the statistics of the observed data that might contain the true value of the unknown population parameter.
Formula used:
For a chi square, the expected frequency fe is given as,
fe=Row marginal×Column marginalN
Where N is the total of frequencies.
The chi square statistic is given by,
χ2(obtained)=∑(fo−fe)2fe
Where fo is the observed frequency,
And fe is the expected frequency.
Calculation:
From the given information,
The observed frequency is given as,
fe=Row marginal×Column marginalN……(1)
Substitute 65 for row marginal, 35 for column marginal and 100 for N in equation (1).
f1=65×35100=22.75
Substitute 65 for row marginal, 65 for column marginal and 100 for N in equation (1).
f1=65×65100=42.25
Substitute 35 for row marginal, 35 for column marginal and 100 for N in equation (1).
f1=35×35100=12.25
Substitute 35 for row marginal, 65 for column marginal and 100 for N in equation (1).
f1=35×65100=22.75
Consider the following table,
6.25 | fo | fe | fo−fe | (fo−fe)2 | (fo−fe)2/fe |
20 | 22.75 | -2.75 | 7.5625 | 0.332417582 | |
45 | 42.25 | 2.75 | 7.5625 | 0.178994083 | |
15 | 12.25 | 2.75 | 7.5625 | 0.617346939 | |
20 | 22.75 | −2.75 | 7.5625 | 0.332417582 | |
Total | 100 | 100 | 0 | χ2=1.46 |
The value fo−fe is obtained as,
Substitute 20 for fo and 22.75 for fe in the above formula.
fo−fe=20−22.75=−2.75
Squaring the above obtained result,
(fo−fe)2=(−2.75)2=7.56
Divide the above obtained result by fe.
(fo−fe)2fe=7.5622.75=0.33
Proceed in a similar manner to obtain rest of the values of (fo−fe)2/fe and refer above table for the rest of the values of (fo−fe)2/fe.
The chi square value is given as,
χ2(obtained)=∑(fo−fe)2fe=0.33+0.18+0.62+0.33=1.46
Thus, the chi square value is 1.46.
Conclusion:
The chi square value is 1.46.
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Chapter 10 Solutions
EBK THE ESSENTIALS OF STATISTICS: A TOO
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