Use the data below for this problem, follow instructions to findanswers:

1.64 1.55 1.83 1.94

1.86 1.56 1.56 1.96

1.88 1.92 1.67 1.97

1.69 1.71 1.58 1.99

1.77 1.70 1.84 2.10

1.69 1.59 1.67 1.97

1.58 1.58 1.79 1.88

1.58 1.51 1.61 1.91

1.70 1.68 1.91 2.21

1.71 1.63 1.68 2.01

1.68 1.59 1.76 1.99

1.64 1.83 1.64 1.94

1.68 1.76 1.67 1.98

1.65 1.95 1.76 2.35

1.47 1.61 1.61 1.91

1.80 1.73 1.59 2.10

1.75 1.70 1.65 2.10

1.48 1.63 1.34 1.64

1.59 1.57 1.71 1.89

1.96 1.69 1.75 2.09

2.01 1.57 1.80 2.10

1.67 1.57 1.93 1.97

1.87 1.52 1.77 1.92

2.01 1.61 1.70 2.00

1.59 1.61 1.59 1.89

1.91 1.59 1.61 1.99

1.72 1.77 1.59 1.89

1.51 1.46 1.76 1.81

1.78 1.48 1.79 1.88

1.80 1.54 1.54 1.84

1.93 1.46 1.86 2.23

1.71 1.78 1.56 2.18

1.61 1.70 1.45 1.75

1.70 1.71 1.45 2.00

1.79 1.58 1.79 1.98

1.81 1.65 1.72 2.02

1.92 1.69 1.68 2.22

CASE ASSIGNMENT #2

Please be sure to read the case description for each problembefore you begin the case

assignment. By so doing, you will have a clearer understandingof the purpose of the exercise

and how you will conduct the analysis. This could help reducethe amount of time you spend in

the computer lab on this assignment.

Answer the questions listed in this handout.

Currentprices.com keeps a record of the sales prices of gasoline($/ gallon, at pump) at different

retailing pumps/ locations. The data on regular unleadedgasoline, as recorded at 37 different

pumps at 4 different locations, viz., Allen, Blaze, Corlis, andDustin. The data is presented in the

spreadsheet entitled

Assgt#2.xls

.

You have to: (1) Analyze the data for the existence of anydifference between the true mean

prices at the four different locations using the ANOVAprocedure; (2) conduct Tukey’s multiple

comparison procedure on the data; (3) construct individual 95%confidence intervals for the

mean price of regular gasoline in the four locations; and (4)construct a family of simultaneous

95% confidence intervals for the six possible pairwisedifferences between the mean prices in the

four locations. The general procedure is outlined below.

1. Open the file Assgt#2.xls.

2. Insert a row (under Edit menu) at the top of the spreadsheetthen label the columns A, B, C,

and D appropriately. (Allen, Blaze, Corlis, and Dustin, forexample)

3. To conduct the ANOVA, select

Data > Data Analysis > Anova: Single Factor > Input

Range = A1:D38, Labels in First Row = check > OK

. The output will appear on a new

worksheet.

4. To continue the analysis with pairwise comparisons, transferthe data to Minitab. Minitab is a

statistical package, currently installed in the College ofBusiness Computer lab. You can stop by

the physical computer lab on the 1

st

floor of BLB or access it in the virtual lab via VMWare.

Visit the web site http://www.cob.unt.edu/lab/virtuallab.php forinstructions on how to access the

virtual lab from home, using your PC or Mac. Once in the COBcomputer lab, select the

Coba

Menu > DSCI > Minitab

, or

COB Menu (Star Icon) > Statistics> Minitab

. Copy the data in the

four columns in Excel (A1:D38), and paste it in Minitab’s topleft cell (the gray cell that holds

the header for column C1).

5. Select

Stat > ANOVA > One Way > Response data are in aseparate column for each

factor level > Responses = Allen Blaze Corlis Dustin

.

Select the

Comparisons

button. Then select

Tukey = check

and

Tests = check, > OK > OK

.

ANOVA output will appear in Minitab’s Session window. The outputincludes an ANOVA table

just like the one you got in Excel. Also included is a list ofthe four locations with corresponding

95% Confidence Intervals for the mean gasoline prices.

The output continues with information on Tukey pairwisecomparisons. At the top, grouping

information is presented. Locations that share the same groupcode (e.g. A, B, etc.) are grouped

together, i.e., do not have significantly different meangasoline prices. At the bottom of the

pairwise comparisons output, point estimates and confidenceintervals for mean price differences

between the 6 possible location pairs are presented. Pointestimates that are positive signify that

the location that gets subtracted in the difference has asmaller mean gasoline price, and vice

versa. Intervals that include 0 signify pairs of locations wherethe mean gasoline prices are not

significantly different.

1) What is the lower limit of the 95% confidence interval forthe difference in true mean gasoline prices in Dustin andBlaze?

a) 1.78
b) 1.69
c) 0.346
d) 0.41
e) 0.29

2) What is the best estimate for the true mean price of gas inBlaze?

a) $0.00
b) $1.99
c) $1.64
d) $1.73
e) $1.68

3) The decision, conclusion, and reason for the conclusion ofthe test of the difference in gasoline prices using ANOVA is:

F.T.R. Ho, conclude there is evidence of gasoline price differencesbecause F calculated is < F critical
F.T.R. Ho, conclude there is no evidence of gasoline pricedifference because F calculated is < F critical
Reject Ho, conclude there is no evidence of gasoline pricedifferences because F calculated is > F critical
Reject Ho, conclude there is evidence of gasoline price differencebecause F calculated is > F critical
Reject Ho, conclude there is evidence of gasoline price differencesbecause p value is > F critical

4) What is the calculated value of the test statistic fortesting the equality of gas prices in the four counties(overall)?

a. 2.67
b. 0.017
c. 0.05
d. 52.13
e. 2.49

5) What is the estimate of the pooled variance (of error) for theabove model of gas prices?

a. 2.49
b. 0.05
c. 52.13
d. 2.67
e. 0.017