Question

If you wanted to calculate a 90% confidence interval for the difference in average
number of friendship contacts between primary aged boys and girls and we are
pretending that df=12, what t scores would you use? (assuming equal variances again)
A. ☐+/- 1.356
B. ☐+/- 2.681
C. ☐+/- 1.782
D. ☐+/- 2.179
E. ☐+/- 3.055
Suppose you calculated your 90% interval as described above and your lower
confidence limit was
–2.75 and your upper confidence limit was 3.20. What would that mean?
A. ☐It would mean that boys have 2.75 fewer contacts than girls on average
B. ☐It means that girls have 8.95 more contacts on average than boys
C. ☐It means that there may be no difference between the average number of
contacts for boys and girls
D. ☐It means that girls definitely have more contacts than boys
E. ☐It means that girls have 3.20 times more friendship contacts than boys
If you were to increase your confidence level to 99%, holding everything else
constant
A. ☐Your interval would be more precise
B. ☐You would be less likely to miss the population value
C. ☐Your interval would be wider
D. ☐You would have less confidence
E. ☐You would have to change your df

Answer 1

1).the t scores i will use:-

[ steps:-

in any blank cell of excel ype =T.INV.2T(0.1,12) press enter]

2).it would mean that:-

It means that there may be no difference between the average number of
contacts for boys and girls (C)

[ explanation:-

hypothesis:-

3).If you were to increase your confidence level to 99%, holding everything else constant, then :-

Your interval would be wider (C)

[ explanation:-

we know that as confidence level increases confidence interval becomes wider, in order to be more confident.]

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