The use of cellular phones in automobiles has increased dram

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. (Round your answers to 3 decimal places.)

Solution

a)

With df = (a - 1)(b - 1), where a and b are the number of categories of each variable,          
          
a =    2      
b =    2      
          
df =    1      
          
Thus, the critical value is          
          
significance level =    0.05      
          
chi^2(critical) =    3.841458821      

Hence, reject Ho if chi^2 > 3.841458821. [ANSWER]

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b)

Doing an Expected Value Chart,          
          
31.62162162   228.3783784  
58.37837838   421.6216216  
          
Using chi^2 = Sum[(O - E)^2/E],          
          
chi^2 =    44.69921105   [ANSWER]

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As chi^2 > 3.8414, we   REJECT THE NULL HYPOTHESIS.      
          
REJECT H0. There IS A relationship between phone use and accidents. [conclusion]