Reference no: EM13236470

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.