Question

3)Johnson et al (A-16) performed a retrospective review of 50 fetuses that underwent open fetal myelomeningocele closure. The data below shw the gestational age in weeks of the 50 fetuses undergoing the prodecure.

25 25 26 27 29 29 29 30 30 31 32 32 32 33 33 33 33 34 34 34 35 35 35 35 35 35 35 35 35 36 36 36 36 36 36 36 36 36 36 36 36 36 36 36 36 36 36 36 37 37

a) construct a stem-and leaf plot for these gestational ages.

b)Based on the Stem- and leaf plot, what one worn would you use to describe the nature of the date?

c)why do you think the stem and leaf plot look the way it does?

d)compute the mean, median, variance, and standard deviation.

Answer 1

a) Stem and leaf plot:

Stem	Leaf
2	5 5 6 7 9 9 9
3	0 0 1 2 2 2 3 3 3 3 4 4 4 5 5 5 5 5 5 5 5 5 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 7 7

b) The data is left skewed.

c) The stem and leaf plot looks like this beacuse the most of the ponts lie in the right handside of the distribution.

d)

∑x = 1684

∑x² = 57222

n = 50

Mean , x̅ = Ʃx/n = 1684/50 = 33.68

Median = (25th + 26th value of sorted data)/2 = (35+35)/2 = 35

Variance, s² = (Ʃx² - (Ʃx)²/n)/(n-1) = (57222-(1684)²/50)/(50-1) = 10.3037

Standard deviation, s = √[(Ʃx² - (Ʃx)²/n)/(n-1)] = √[(57222-(1684)²/50)/(50-1)] = 3.21