Standard Deviation

Question

Suppose you counted the number of people in line each time you came to your favourite coffee shop last month. Here are the results of your investigation. What is the error determined bt the 2/3 rule?

NUMBER OF PEOPLE: |0 |1 |2 |3 |4 |5 |6 |7 |8 |9 |10

OCCURRENCES: |1 |3 |3 |4 |5 |8 |5 |4 |3 |2 |1

Answer 1

If I understand the question correctly.

For this case:

n=11

mean=3.54

σ=1.924

Range for ± one σ from mean≈ 1.6-5.5

8 data points out of 11 fall in the range or ≈ 72%

2/3 ≈ 67%, So the error would be 5%.