excerise 29) The mean speed of a sample of vehicles along a stretch of highway i

Question

excerise 29) The mean speed of a sample of vehicles along a stretch of highway is 67 miles per hour ,with a standard deviation of 4 miles per hour ,Estimate the percent of vehicles whose speeds are between 63 miles per hour and 71 miles per hour .( Assume the date set has a bell -shaped distribution .)

exercise 33) the speeds for eight more vehicles are listed .Using the sample statistics from excercise 29.determine which of the data entries are unsual .Are any of the data entries very unsual ? explain your reasoning

70,78,62,71,65,76,82,64

Explanation / Answer

29.) X : Speed of the vehicle

P(63 < X < 71)

= P((63 -67)/4 < Z < (71 - 67)/4)

= P ( -1 < Z < 1)

= P(Z < 1) - P(Z < -1)

= 0.8413 - 0.1587

= 0.6826

68.26% of vehicles have speed between 63 miles per hour and 71 miles per hour.

33.)

78,82 is a sample value which is very unusual because it is very different from the sample mean

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