# Sampling question 2

• Jul 14th 2006, 09:12 PM
kingkaisai2
Sampling question 2
The masses of kilogram bags of flour produced in a lottery have a normal distribution with mean 1.005 kg and standard deviation 0.0082 kg. A shelf in a store is loaded with 22 of these bags assumed to be randomn sample.

a)Find the probability that a randomly chosen bag has mass less than 1 kg.
b) Find the probability that the mean mass of 22 bags is less than 1 kg.

State giving a reason, which of the above answers would be little changed if the distribution of masses were not normal.
• Jul 15th 2006, 06:07 AM
galactus
To find probabilities for individual members of a population use the formula:

$z=\frac{x-{\mu}}{\sigma}$

To find probabilites for the mean of a sample size use:

$z=\frac{x-{\mu}}{\frac{\sigma}{\sqrt{n}}}}$