Question

1) In 2003, the American Psychological Association conduced a survey of a random sample of psychologists with various academic degrees and levels of experience. Of the 31 psychologists who received a masters degree in 2003, the mean income was $43,834 with a standard deviation of $16,870. Use this information to construct a 99% confidence interval for the average salary of psychologists receiving masters degrees in 2003.

2)In 2003, the American Psychological Association conduced a survey of a random sample of psychologists with various academic degrees and levels of experience. Of the 31 psychologists who received a masters degree in 2003, the mean income was $43,834 with a standard deviation of $16,870. Use this information to construct a 90% confidence interval for the average salary of psychologists receiving masters degrees in 2003.

Answer 1

Q 1 ) we want to construct 99% confidence interval for the average salary of psychologists receiving masters degrees in 2003.

Given that

Sample mean

Sample SD

Sample size

Confidence level

99% C.I for mean is

Where ,

DF = n - 1 = 31 - 1= 30

tc = 2.750 ..............( From t table )

99% C.I for mean is

.....................(Answer)

99% confidence interval for the average salary of psychologists receiving masters degrees in 2003 is ...................(Answer)

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Q 2) we want to construct 90% confidence interval for the average salary of psychologists receiving masters degrees in 2003.

Given that

Sample mean

Sample SD

Sample size

Confidence level

90% C.I for mean is

Where ,

DF = n - 1 = 31 - 1= 30

..............( From t table )

90% C.I for mean is

.....................(Answer)

The 90% confidence interval for the average salary of psychologists receiving masters degrees in 2003 is ...................(Answer)