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  #1  
Old 01-05-2013
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Stats Calculating the 95% Confidence Interval

A study is conducted to evaluate iq for patients with various types of schizophrenia. Twenty patients were dropped from sample because they couldn t complete two or more portions of test. Four additional patients refused to take test. Results for the 100 patients who completed the test showed an average IQ of 110 with a standart deviation of 20. Which of the following is the best estimate of the 95% confidence interval for the sample ?

A 70 to 130
B 70 to 150
C 85 to 115
D 90 to 130
E 105 to 115
F 106 to 114
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  #2  
Old 01-05-2013
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F) 106 to 114
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  #3  
Old 01-05-2013
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Default B

I would pick B
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  #4  
Old 01-06-2013
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Default B

B 70 to 150
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  #5  
Old 01-07-2013
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F.

mean +/- 1.96 x SD/square root (N)

110+1.96 x 20/ Squroot 100 = 113.9
100-1.96 x 20/ Squroot 100 = 106

therefore we can say with 95% confidence that the values are btw 106 to 114.
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Old 01-07-2013
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Default F

Agreed with above calculations F is my answer also
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  #7  
Old 01-17-2013
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F is correct
When i was picking the answer made the same mistake of choosing B which is the iq according to test results with two sd deviation above and below
Where as question was asking for CI
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  #8  
Old 01-17-2013
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made the same mistake and answered B ..... you are right it's F
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