A newspaper article reported that people spend a mean of 6 hours per day watchin

Question

A newspaper article reported that people spend a mean of 6 hours per day watching TV, with a standard deviation of 1.8 hours. A psychologist would like to conduct interviews with the 20% of the population who spend the most time watching TV. She assumes that the daily time people spend watching TV is normally distributed. At least how many hours of daily TV watching are necessary for a person to be eligible for the interview? Carry your intermediate computations to at least four decimal places. Round your answer to at least one decimal place.

Explanation / Answer

First, we get the z score from the given left tailed area. As          
          
Left tailed area = 1 - 0.20 =   0.8      
          
Then, using table or technology,          
          
z =    0.841621234      
          
As x = u + z * s,          
          
where          
          
u = mean =    6      
z = the critical z score =    0.841621234      
s = standard deviation =    1.8      
          
Then          
          
x = critical value =    7.51491822  HOURS [ANSWER]  

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