The braking ability of two types of automobiles was compared. Random samples of 64 auto mobiles were tested for each type. The recorded measurement was the distance required to stop when the brakes were applied at 40 miles per hour. The computed sample means and variances were as follows: y¯¯¯1=118,y¯¯¯2=109 s21=102,s22=87
. Do the data provide sufficient evidence to indicate a difference in the mean stopping distances of the two types of automobiles? Give the attained significance level.

The data provide sufficient evidence to indicate a difference in the mean stopping distances of the two types of automobiles

Step-by-step explanation:

Formulate the null and alternate hypothesis as

H0: u1= u2  against the claim Ha: u1≠ u2

The data given is

y`1=118,    y`2=109     s21=102,   s22=87

The test statistic used is t= y1`- y2`/ Sp√1/n1+ 1/n2

n1= n2= 64

And

Sp² = (n1-1) s12 + (n2-1) s22 / n1+n2-2

Sp² = 63*102+6*87/64+64-2

Sp² = 94.5

Sp= 9.7211

Putting the values in the test statistic

t= 118-108/9.7211√1/64+1/64

t= 5.237

Now finding the value of t at ∝=0.01 for two tailed test

t( 126,0.005)= ±2.6154

At alpha= 0.01  the null hypothesis is rejected.

Now finding the value of t at ∝=0.05 for two tailed test

t( 126,0.025)= ±1.979

Even at alpha= 0.05 the null hypothesis is rejected.

Also at alpha= 0.05 the null hypothesis is rejected because the critical value is  ±1.657

Hence it is concluded that the data provide sufficient evidence to indicate a difference in the mean stopping distances of the two types of automobiles

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