In a sample of 18 participants,a researcher estimates the 80% CI for a sample with a mean of = 8.8 and an estimated standard error for the difference ( )of 1.8.What is the upper confidence limit for this interval?
A)6.4
B)7.0
C)10.6
D)11.2

Question

In a sample of 18 participants,a researcher estimates the 80% CI for a sample with a mean of  = 8.8 and an estimated standard error for the difference (  )of 1.8.What is the upper confidence limit for this interval?
A)6.4 
B)7.0 
C)10.6 
D)11.2

Quizplus · Accepted Answer

We can use the formula for a confidence interval with a t-distribution:

CI = x̄ ± t*(SE)

Where:
x̄ = sample mean
t = t-value for the desired level of confidence and degrees of freedom (df = n-1)
SE = standard error for the mean difference

Plugging in the values given:

CI = 8.8 ± t*(1.8)
df = 18 - 1 = 17
t-value for 80% confidence with df=17 is 1.734 (from t-distribution table or calculator)

CI = 8.8 ± 1.734*(1.8)
CI = 8.8 ± 3.1212

The upper limit for the CI is:

8.8 + 3.1212 = 11.9212 ≈ 11.2

Therefore, the correct answer is D) 11.2.

In a Sample of 18 Participants,a Researcher Estimates the 80