Part A: Analysis of traffic data
In this section you will use the data you collected in Assignment 1.
|
Car Size (m^3)
|
Body
|
Year
|
Year
|
|
9.941
|
Small Cars
|
2003
|
Less than 2005
|
|
10.251
|
Small Cars
|
1996
|
Less than 2005
|
|
10.699
|
Small Cars
|
2012
|
Greater than 2005
|
|
9.139
|
Medium Cars
|
1972
|
Less than 2005
|
|
10.426
|
Medium Cars
|
1986
|
Less than 2005
|
|
11.304
|
Medium Cars
|
2001
|
Less than 2005
|
|
12.255
|
Medium Cars
|
2007
|
Greater than 2005
|
|
12.332
|
Medium Cars
|
2007
|
Greater than 2005
|
|
13.305
|
Large Cars
|
2004
|
Less than 2005
|
|
13.387
|
Large Cars
|
2004
|
Less than 2005
|
|
13.955
|
Large Cars
|
2004
|
Less than 2005
|
|
13.402
|
Large Cars
|
2011
|
Greater than 2005
|
|
13.470
|
Large Cars
|
2011
|
Greater than 2005
|
|
13.484
|
Large Cars
|
2010
|
Greater than 2005
|
|
14.618
|
Luxury Cars
|
2010
|
Greater than 2005
|
|
14.987
|
Luxury Cars
|
2010
|
Greater than 2005
|
|
13.814
|
Luxury Cars
|
2002
|
Less than 2005
|
|
14.278
|
Luxury Cars
|
2002
|
Less than 2005
|
1. Comparing two means:
a) Confidence interval for difference between means
(i) Use Minitab to construct a 95% Confidence Interval for the difference between the means of your numeric variable for the different levels of your 2-level categorical variable.
(ii) Interpret your confidence interval in context (remember units).
(iii) Use your confidence interval to draw a conclusion about the difference (if any) between the two levels of your categorical variable.
b) Two-tailed hypothesis test for the difference between two means
(i) State the null and alternative hypotheses (in words and symbols) for testing if there is a significant difference between the means of your numeric variable for the different levels of your 2-level categorical variable.
(ii) Use Minitab to carry out the test. State the test statistic and corresponding p-value for these hypotheses.
(iii) Explain whether you have evidence for or against the null hypothesis.
(iv) State your conclusion in a form that a non-statistician would understand.