SD of zero means all the ratings were the same, so what do think those rating were if their mean was 4?

On the second day, another 15 persons were given the taste test. The feedback gathered from the total random sample of 18 persons is shown in the frequency table below:Rating

1

2

3

4

5

6

7

Frequency

3

7

3

3

1

1

0

- What is the estimated mean of the ratings?

- What is the estimated standard deviation of the ratings?

where

and:

CB