Do you know the 68, 95, 99.7 rule?
Can you help me with the following problem. I can work out that the variation is 2 standard deviations from the mean but how do I know that includes 95% of results?
A store manager determined the store's mean daily receipts as $550 with standard deviation of $200. On what proportion of days were the daily receipts between $150 and $950?