Given:
Mean = 7.5 hours
Standard deviation = 2.0 hours
Interview 20% of the population
Let x = daily time people spend watching TV.
Therefore, The z score probability distribution for normal distribution is given by:
Where:
μ = mean = 7.5 hours
σ = standard deviation = 2.0 hours
Using the table of the critical value we find the z value for the top 20%.
Next, substitute the given values in the formula of z:
And solve for x:
Therefore, at least 9.2 hours of daily TV watching is necessary for a person to be eligible for the interview.
Answer: 9.2 hours per day