Question

Suppose the age that children learn to walk is normally distributed with mean 12 months and standard deviation 2.5 month. 34 randomly selected people were asked what age they learned to walk. Round all answers to 4 decimal places where possible.

Answer 1

Explanation:

a.) it's just mean, variance

so here it's just 12,6.25

b.) For the x bar thing just divide the variance by the number of people (mean stay the same)

the variance is then (2.5²/34)= .1838

which makes it (12,.1838)

c.) here we don't use x bar (and so it's normal (12,2.5²))

p(11.6) = (11.6-12)/(2.5)= -.16 = .4364

p(12.4)= (12.4-12)/2.5 = .16= .5636

.5636-.4364= .1272

d.) here we use x bar because it's asking for an average so it's normal (12, .1838)

same deal

p(11.6)=(11.6-12)/√.1838= -.93295= .1762

p(12.4)= (12.4-12)/√.1838= .93295= .8238

.8238-.1762= .6476

d.) no because they're probably IID

f.) It's average so here we use x bar

q1 is just the 25th percentile

the 25th percentile is -.6745

-.6745=(x-12)/(√.1838)= 11.711

q3 is the 75th percentile

.6745=(x-12)/√.1838

x=12.289

The interquartile range is just the difference between the two

12.289-11.711= .5784