In following question a simple random sample of size n 6 30 for a quantitative variable has been obtained. Using the normal probability plot, the correlation between the variable and expected z-score, and the boxplot, judge whether a t-interval should be constructed.

1. n = 12; Correlation = 0.987

(a)

(b)

2. n = 15; Correlation = 0.893

3. n = 13; Correlation = 0.966

4. n = 9; Correlation = 0.997

15 05 -05 -1 -15 30 35 40 45 50 55 Expected z-Score 30 35 40 45 5o 55