Introductory Statistics 161 Assignment 2
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 [4 Marks]
(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 [4 Marks]
(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…