It is known that driving can be difficult in regions where winter conditions inv
ID: 3219988 • Letter: I
Question
It is known that driving can be difficult in regions where winter conditions involve snow-covered roads. For cars equipped with all-season tires traveling at 90 kilometers per hour, the mean stopping time in fresh snow is known to be 215 meters, with a standard deviation of = 2.5 meters. It is often advocated that automobiles in such areas should be equipped with special tires to compensate for such conditions, especially with respect to stopping distance. A manufacturer of tires made for driving in fresh snow claims that vehicles equipped with their tires have a decreased stopping distance. A study was done using a random sample of nine snow tires from the manufacturer on a snow-covered test track. The tests resulted in a mean stopping distance of = 212.9 meters. What is the P-value?
Not within ± 0.002 of any of the above 0.012 0.050 0.025 0.006Explanation / Answer
here n=9
hence std error =std deviation/(n)1/2 =0.833
hence tes tstat z=(X-mean)/std error =(212.9-215)/0.833 =-2.52
for above left tailed test p value =0.006
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