In: Statistics and Probability
The amounts of nicotine in a certain brand of cigarette are
normally distributed with a mean of 0.962 g and a standard
deviation of 0.313 g. The company that produces these cigarettes
claims that it has now reduced the amount of nicotine. The
supporting evidence consists of a sample of 48 cigarettes with a
mean nicotine amount of 0.899 g.
Assuming that the given mean and standard deviation have
NOT changed, find the probability of randomly seleting 48
cigarettes with a mean of 0.899 g or
less.
Enter your answer as a number accurate to 4 decimal places.
Based on the result above, is it valid to claim that the amount of
nicotine is lower?
Solution :
Given that ,
mean =
= 0.962 g
standard deviation =
= 0.313 g
n = 48
=
= 0.962 g
=
/
n = 0.313 /
48 = 0.0452
P(
0.899 ) = P((
-
) /
(0.899 - 0.962) / 0.0452 )
= P(z
-1.39)
Using z table
= 0.0823
No. The probability of obtaining this data is high enough (greater than a 5% chance) to have been a chance occurrence.