Quiz 6 solutions
1)
1.
Null: a) Data can be due to chance."
b) Data is like drawing 225 times from a box with an average of
3.5
(or "average of school district is 3.5")
2.
Alternative: a) Data cannot be explained by chance.
b) The average is greater than 3.5.
3.
Z: SEavg = sqrt(225)*.5/225 = .0333,
z=(3.83.5)/.0333 = 9
4.
P: P very close to 0%
5.
Conclusion: a) data cannot be explained by chance,
b) reject null
c) students in the school district did better than the state average.
2.)
1. Null: Data can be explained by chance. The refrigerator has not been
damaged.
Data is like drawing 5 times from a box with an average of 0 (or 36)
2. Alternative: The data cannot be explained by chance.
The average is greater than 0 (or 36)
3. T:
Avg: (.5+.75+0+1+.15)/5 = .48
SD = sqrt ((1/5)(.5^2+.75^2+0^2+1^2+.15^2).48^2) = .369
SD+ = sqrt(5/4)*.369 = .4132
SE = sqrt(5)*.4132/5 = .184797
T = (.480)/.184797 = 2.597
4. P calculation:
Degrees of freedom = 51 =4
P: 2.5% < p < 5%
5. Conclusion: doesn't look like chance, Reject null at 5% level, looks like
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 Spring '09
 IBSER
 Statistics, Leftwing politics, chance, SQRT

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