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Stats Homework #6
April 20, 2008
7.20
a.
What are the degrees of freedom?
n1=151=14
Degrees of freedom = 14
b.
Give two critical values t* from Table D that bracket t.
t is between t*=2.145 (p= .025) and t*=2.264 (p=.02)
c. What arte the right tailed probabilities p for these two entries?
t is between t*=2.145 (p= .025) and t*=2.264 (p=.02)
d.
Between what two values does the Pvalue of the test fall?
.025 < P < .02
e. Sketch distribution for this exercise. Illustrate answers to part c and d.
f. Is the value of t = 2.15 significant at the 5% level? Is it significant at the 1% level?
7.34 EXAMPLE ON PAGE 453
a. Calculate the same mean x and its standard error.
Sample Mean x
5.6+5.1+4.6+4.8+5.7+6.4=32.2
32.2 / 6 = 5.367
Standard Error
5.65.4= .2
=. 04
5.15.4= .3 = .09
4.65.4= .8 = .64
4.85.4= .6 = .36
5.75.4= .3 = .09
6.45.4= 1 = 1
.66 / 2.44 = .269
b. Use the t procedures to give a 90% confidence interval for this patient’s means
phosphate level.
From Table D we find that t* = 2.015. The 90% confidence interval is
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 Spring '08
 Stein
 Statistics, Degrees Of Freedom

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