Question

Which distribution should you use for this problem?

Short answer

The distribution for this problem is$N\left(2.2,\frac{0.2}{\sqrt{20}}\right)$.

Step-by-step solution

Given Information 

The weight of each head of lettuce was then recorded. The mean weight was $2.2$pounds with a standard deviation of $0.1$pounds. The population standard deviation is known to be $0.2$pounds.

Explanation

The mean and standard deviation are the two parameters of a conventional normal distribution. In a normal distribution, $68\%$ percent of the observations are within one standard deviation of the mean,$95$ percent are within two standard deviations, and $99.7\%$are within three standard deviations. For this problem we should use normal distribution with parameters:

$N\left(\mu ,\frac{\sigma }{\sqrt{n}}\right)$

Where,

$\mu =2.2$

and

$\frac{\sigma }{\sqrt{n}}=\frac{0.2}{\sqrt{20}}$