a)
Margin of error = Width of confidence interval / 2
= (235.4 - 197.2) / 2
= 19.1
b)
df= n - 1 = 27 - 1 = 26
From T table,
t critical value at 0.04 significance level with 26 df = 2.162
c)
Margin of error = t * Standard error
19.1 = 2.162 * SE
SE = 8.83
d)
Standard error = Standard deviation / sqrt (n)
Standard deviation = SE * sqrt (n)
= 8.83 * sqrt (27)
= 45.88
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