The average amount of time people spend on facebook each day is 71 minutes, with a standard deviation of 4.7 minutes. Are you more likely to select a random person that spends less than 68 minutes per day, or a group of 35 people that spend on average less than 65 minutes per day on facebook? Assume this is normally distributed. Find the chances of each to decided which is more likely by how much.

Answer 1

For the individual,

Z = (score-mean)/SD

For the group,

Z = (score-mean)/SEm

SEm = SD/√n

For both, find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportions related to the Z scores.