In: Statistics and Probability
The use of cellular phones in automobiles has increased dramatically in the last few years. Of concern to traffic experts, as well as manufacturers of cellular phones, is the effect on accident rates. Is someone who is using a cellular phone more likely to be involved in a traffic accident? What is your conclusion from the following sample information? Use the 0.05 significance level.
Had Accident in the Last Year | Did Not Have an Accident in the Last Year | |
Uses a cell phone | 46 | 404 |
Does not use a cell phone | 19 | 268 |
Click here for the Excel Data File
H0: There is no relationship between phone use and accidents.
H1: There is a relationship between phone use and accidents.
State the decision rule using 0.05 significance level. (Round your answer to 3 decimal places.)
Compute the value of chi-square. (Round your answer to 3 decimal places.)
What is your decision regarding H0?
Significance level : =0.05
Degrees of freedom = (Number rows-1) x (Number of columns-1)=(2-1)x(2-1)=1
Critical value of for 1 degree of freedom = 3.841
If value of the test statistic is greater than the critical value : 3.841 ; Reject the null hypothesis; Otherwise fail to reject the null hypothesis.
Test Statistic
O : Observed Frequency
E: Expected Frequency
Observed Counts/Frequency | Had Accident in the Last Year | Did Not Have an Accident in the Last Year | Row Total |
Uses a cell phone | 46 | 404 | 450 |
Does not use a cell phone | 19 | 268 | 287 |
Column Total | 65 | 672 | Grand Total =737 |
E: Expected Count/Frequency | Had Accident in the Last Year | Did Not Have an Accident in the Last Year |
Uses a cell phone | (450*65) / 737 | (450*672) / 737 |
Does not use a cell phone | (287*65) / 737 | (287*672) / 737 |
E: Expected Count/Frequency | Had Accident in the Last Year | Did Not Have an Accident in the Last Year |
Uses a cell phone | 39.6879 | 410.3121 |
Does not use a cell phone | 25.3121 | 261.6879 |
O | E | O-E | ||
46 | 39.6879 | 6.3121 | 39.8423 | 1.0039 |
404 | 410.3121 | -6.3121 | 39.8423 | 0.0971 |
19 | 25.3121 | -6.3121 | 39.8423 | 1.5740 |
268 | 261.6879 | 6.3121 | 39.8423 | 0.1523 |
value of chi-square = 2.827
As value of the test statistic: 2.827 < the critical value : 3.841 ; fail to reject the null hypothesis.
There is not sufficient evidence to conclude that There is a relationship between phone use and accidents.
Therefore,
Is someone who is using a cellular phone more likely to be involved in a traffic accident? No evidence with the given data.