Question
A psychologist is interested in the mean IQ score of a given group of children. It...
A psychologist is interested in the mean IQ score of a given group of children. It is known that the IQ scores of the group have a standard deviation of 12. The psychologist randomly selects 80 children from this group and finds that their mean IQ score is 112. Based on this sample, find a 90% confidence interval for the true mean IQ score for all children of this group. Then complete the table below.
Carry your intermediate computations to at least three decimal places. Round your answers to one decimal place.
A. What is the lower limit of the 90% confidence interval?
B. What is the upper limit of the 90% confidence interval?
Homework Answers
Answer #1
90% confidence interval for 
is
- Z
/2
* 
/ sqrt(n) <
<
+ Z/2
*
/ sqrt(n)
112 - 1.645 * 12 / sqrt(80) <
< 112 + 1.645 * 12 / sqrt(80)
109.8 <
< 114.2
A) Lower limit = 109.8
B) Upper limit = 114.2
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