Alert nurses at the Veteran\'s Affairs Medical Center in Northampton, Massachuse
ID: 3125043 • Letter: A
Question
Alert nurses at the Veteran's Affairs Medical Center in Northampton, Massachusetts, noticed an unusually high number of deaths at times when another nurse, Kristen Gilbert, was working. Kristen Gilbert was arrested and charged with four counts of murder and two counts of attempted murder. When seeking a grand jury indictment, prosecutors provided a key piece of evidence consisting of the table below. Use a 0.01 significance level to test the defense claim that deaths on shifts are independent of whether Gilbert was working. Shifts With a Death Shifts Without a Death Gilbert Was Working 40 217 Gilbert Was Not Working 34 1350 4. Calculate the 2 test statistic. Solution: Instructor Comments: 5. Calculate the 2 critical value. Solution: Instructor Comments: 6. Is there sufficient evidence to reject the defense claim that deaths on shifts are independent of whether Gilbert was working? Solution: Instructor Comments:
Explanation / Answer
Alert nurses at the Veteran's Affairs Medical Center in Northampton, Massachusetts, noticed an unusually high number of deaths at times when another nurse, Kristen Gilbert, was working. Kristen Gilbert was arrested and charged with four counts of murder and two counts of attempted murder. When seeking a grand jury indictment, prosecutors provided a key piece of evidence consisting of the table below. Use a 0.01 significance level to test the defense claim that deaths on shifts are independent of whether Gilbert was working.
Shifts With a Death Shifts Without a Death
Gilbert Was Working 40 217
Gilbert Was Not Working 34 1350
4. Calculate the 2 test statistic.
Solution: 86.481
5. Calculate the 2 critical value.
Solution: 6.635
6. Is there sufficient evidence to reject the defense claim that deaths on shifts are independent of whether Gilbert was working?
Solution: calculated chi square =86.481 > 6.635 the table value.
The null hypothesis is rejected. There is sufficient evidence to reject the defense claim that deaths on shifts are independent of whether Gilbert was working.
Chi-Square Test
Observed Frequencies
Column variable
Calculations
Row variable
C1
C2
Total
fo-fe
R1
40
217
257
28.4107
-28.4107
R2
34
1350
1384
-28.4107
28.4107
Total
74
1567
1641
Expected Frequencies
Column variable
Row variable
C1
C2
Total
(fo-fe)^2/fe
R1
11.5893
245.4107
257
69.6480
3.2891
R2
62.4107
1321.5893
1384
12.9332
0.6108
Total
74
1567
1641
Data
Level of Significance
0.01
Number of Rows
2
Number of Columns
2
Degrees of Freedom
1
Results
Critical Value
6.635
Chi-Square Test Statistic
86.481
Chi-Square Test
Observed Frequencies
Column variable
Calculations
Row variable
C1
C2
Total
fo-fe
R1
40
217
257
28.4107
-28.4107
R2
34
1350
1384
-28.4107
28.4107
Total
74
1567
1641
Expected Frequencies
Column variable
Row variable
C1
C2
Total
(fo-fe)^2/fe
R1
11.5893
245.4107
257
69.6480
3.2891
R2
62.4107
1321.5893
1384
12.9332
0.6108
Total
74
1567
1641
Data
Level of Significance
0.01
Number of Rows
2
Number of Columns
2
Degrees of Freedom
1
Results
Critical Value
6.635
Chi-Square Test Statistic
86.481
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