Answer:
The variance is 
Step-by-step explanation:
From the question we are told that
The sample size is n = 21
The sum of squares is 
Generally the variance is mathematically represented as

substituting values


Answer:
R=19
Step-by-step explanation:
R + 237 = 256
subtract 237 from both sides
R=19
Answer:1442
Step-by-step explanation:
Given,
Mean is,
Standard deviation,
,
Margin of error(E) = 0.54,
For 98% level of confidence,
Thus, the sample size would be,