Q 18 Sound it out Phonics is an instructional method in whic

Q 18

Sound it out: Phonics is an instructional method in which children are taught to connect sounds with letters or groups of letters. A sample of 133 first-graders who were learning English were asked to identify as many letter sounds as possible in a period of one minute. The average number of letter sounds identified was 34.21 with a standard deviation of 23.33. Part 1 out of 2 Construct a 99.9% confidence interval for the mean number of letter sounds identified in one minute. Round the answers to two decimal places. [ ]

Solution

Margin of error = 6.66

Lower bound for conf interval at 99.9% = 34.21-6.66 = 24.75

Upper bound for conf interval at 99.9% = 34.21+6.66 = 41.87

conf interval 99.9% = (24.75, 41.87)