Q1) To help identify baby growth patterns which are unusual confidence interval estimate of mean head circumference of all babies that are two months old is constructed. Random sample of 100 babies is obtained and mean head circumference is found to be 40.6 cm with a standard deviation of 1.6 cm. Determine a 90% confidence interval estimate of the mean head circumference of all two-month-old babies.

i) (39.6,41.6)

ii) (39.0,42.2)

iii) (-1.660,1.660)

iv) (-2.656,2.656)

v) None of the above (do allow for slight rounding errors/table differences in choosing your solution)

Q2) Researcher has conducted a 99% confidence interval that is 10 points wide, based on sample of 36 scores.  Suppose that variability among scores stays the same, how large a sample would be required to produce 99% confidence interval that is only 9 points wide?