# Margin of error

• May 31st 2009, 10:43 PM
brumby_3
Margin of error
Anxiety levels are usually elevated in persons with low-esteem, although there are gender differences in the extent to which this is true. In a random sample of 24 17-year olds females with known low self-esteem the average anxiety score on a standard test was 7.62 with a standard deviation of 3.45. Construct a 95% confidence interval for the true mean anxiety score on this scale for 17-year-old females with self-esteem problems. What is the margin of error associated with this confidence interval?

I've already done the 95% confidence interval and got (6.16, 9.08) but I'm a little stuck on the margin of error part. There's a formula Z(standard deviation/square root n).
• May 31st 2009, 11:49 PM
mr fantastic
Quote:

Originally Posted by brumby_3
Anxiety levels are usually elevated in persons with low-esteem, although there are gender differences in the extent to which this is true. In a random sample of 24 17-year olds females with known low self-esteem the average anxiety score on a standard test was 7.62 with a standard deviation of 3.45. Construct a 95% confidence interval for the true mean anxiety score on this scale for 17-year-old females with self-esteem problems. What is the margin of error associated with this confidence interval?

I've already done the 95% confidence interval and got (6.16, 9.08) but I'm a little stuck on the margin of error part. There's a formula Z(standard deviation/square root n).

Read this: Statistics Tutorial: Confidence Interval
• Jun 1st 2009, 06:06 PM
matheagle
I guess we have normality and you're using a t with n-1=23 degrees of freedom? I'm not really happy about using a z (st. normal) with a small sample.