Question

A researcher is interested in the blood folate level of women who live in a population with a high incidence of neural tube defects. He takes a random sample of size n of women aged 18-45 and measures their blood folate levels. He reports the mean and knows the population standard deviation (SD) and variance. He also states that he is 95% confident that the population mean of the blood folate level lies somewhere between 2.4 and 4.6 ng/ml. What is the population standard deviation?

a. 0.5612

b. 2.8061

c. -0.5612

d. -2.8061

e. It is impossible to say from the information given.

Answer 1

e) it is impossible to say from the information given

because given 95% confidence interval for u is 2.4 and 4.6

in a z normal distribution we have

lower bound = x-z (σ/) = 2.4

upper bound = x+ z (σ/)=4.6

by substracting lower bound from upper bound we get the population standard deviation

[x+ Z (σ/) ] - [ x- z (σ/)] = 4.6-2.4

2 z (σ/)= 2.2

σ= (2.2 × )/ 2z

here we know the z value 1.96 but not given the sample n value. so we can't get population sd here.

e) it is impossible to say from the information given.