# Homework Statistic

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```					2. A stockbroker at Critical Securities reported that the mean rate of return on a sample of
10 oil stocks was 12.6 percent with a standard deviation of 3.9 percent. The mean rate of
return on a sample of 8 utility stocks was 10.9 percent with a standard deviation of 3.5
percent. At the .05 significance level, can we conclude that there is more variation in the
oil stocks?
3.In a particular chi-square goodness-of fit test are six categories and 500 observations.
Use the .01 significance level.
a. how many degrees of freedom are there?
b. what is the critical value of chi- square?

4.The null hypothesis and the alternate are:

Ho: the cell categories are equal.
H1: the cell categories are not equal.
Category
f
A
10
B
20
C
30
D
20

a. state the decision rule, using the .05 significance level
b. Compute the value of chi-square.
c. What is your decision regarding H0?
5.
Classic Golf, Inc. manages five courses in the Jacksonville, Florida, area. The director
wishes to study the number of rounds of golf played per weekly at the fice courses. He
gathered the following sample information.
Day            Rounds
Monday            124
Tuesday            74
Wednesday          104
Thursday           98
Friday             120

At the .05 significance level, is there a difference in the number of rounds played by day
of the week?

6. The safety director of Honda USA took samples at random from the file of minor work
related accidents and classified them according to the time the accident took place.
Time            No. of Accidents           Time            No. of Accidents
8 up to 9 a.m.      61                  up to 2 p.m.        7
9 up to 10 a.m.     62                  up to 3 p.m         8
10 up to 11 a.m. 203                     up to 4 p.m.       19
11 up to 12 p.m.     84                  up to 5 p.m.         6

Using the goodness-of-fit test and the .01 level of significane, determine whether the
accidents are evenly distributed throughout the day. Write a brief explanation of your
conclusion.
7. A stock analyst want to determine whether there is difference in the mean rate of return
for three types of stock: utility, retail, and banking stocks. The following output is
obtained
Analysis of Variance
Source           DF           SS        MS        F          P
Factor              2      86.49       43.25 13.09 0.001
Error             13       42.95        3.30
Total             15      129.44
Individual 95% CIs for mean
Based in pooled StDev
Level              N     Mean           StDev---------------------------------------------
Utility           5      17.400          1.916
Retail            5      11.620          0.356 (------------*------------)
Banking          6       15.400          2.356
--------------*---------------*--------------*-------
---
Pooled StDev =            1.818                         12.0              15.0             18.0

a. using the .05 level of significance, is there a difference in the mean rate of return
among the three types of stock?
b. suppose the null hypothesis is rejected. Can the analyst conclude there is a difference
between the mean rates of return for the utility and the retail stocks? explain

```
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 views: 84 posted: 10/29/2011 language: English pages: 2