Question

Students in a representative sample of 69 second-year students selected from a large university in England participated in a study of academic procrastination. Each student in the sample completed the Tuckman Procrastination Scale, which measures procrastination tendencies. Scores on this scale can range from 16 to 64, with scores over 40 indicating higher levels of procrastination. For the 69 second-year students in the study at the university, the sample mean procrastination score was 41.00 and the sample standard deviation was 6.89.

Construct a 95% confidence interval estimate of μ, the mean procrastination scale for first-year students at this terval college.

Answer 1

95% confidence interval estimate of μ, the mean procrastination scale for second-year students at this terval college is [39.34 , 42.66].

Explanation:

We are given that for the 69 second-year students in the study at the university, the sample mean procrastination score was 41.00 and the sample standard deviation was 6.89.

Firstly, the pivotal quantity for 95% confidence interval for the true mean is given by;

P.Q. =
`(\bar X -\mu)/((s)/(√(n) ) )` ~
`t_n_-_1`

where,
`\bar X` = sample mean procrastination score = 41

s = sample standard deviation = 6.89

n = sample of students = 69

`\mu` = population mean estimate

Here for constructing 95% confidence interval we have used One-sample t test statistics because we don't know about population standard deviation.

So, 95% confidence interval for the true mean,
`\mu` is ;

P(-1.9973 <
`t_6_8` < 1.9973) = 0.95 {As the critical value of t at 68 degree

of freedom are -1.9973 & 1.9973 with P = 2.5%}

P(-1.9973 <
`(\bar X -\mu)/((s)/(√(n) ) )` < 1.9973) = 0.95

P(
`-1.9973 *{(s)/(√(n) ) }` <
`{\bar X -\mu}` <
`1.9973 *{(s)/(√(n) ) }` ) = 0.95

P(
`\bar X-1.9973 *{(s)/(√(n) ) }` <
`\mu` <
`\bar X+1.9973 *{(s)/(√(n) ) }` ) = 0.95

95% confidence interval for
`\mu` =[
`\bar X-1.9973 *{(s)/(√(n) ) }` ,
`\bar X+1.9973 *{(s)/(√(n) ) }`]

= [
`41-1.9973 *{(6.89)/(√(69) ) }` ,
`41+1.9973 *{(6.89)/(√(69) ) }` ]

= [39.34 , 42.66]

Therefore, 95% confidence interval estimate of μ, the mean procrastination scale for second-year students at this terval college is [39.34 , 42.66].