Question

The accompanying data represent the miles per gallon of a random sample of cars with a​ three-cylinder, 1.0 liter engine.

​(a) compute the​ z-score corresponding to the individual who obtained 37.8 miles per gallon. interpret this result.
​(b) determine the quartiles.
​(c) compute and interpret the interquartile​ range, iqr.
​(d) determine the lower and upper fences. are there any​outliers?
31.5 36.0 37.8 38.5 40.1 42.2
34.2 36.2 38.1 38.7 40.6 42.5
34.7 37.3 38.2 39.5 41.4 43.4
35.6 37.6 38.4 39.6 41.7 49.3
the​ z-score corresponding to the individual is
and indicates that the data value is
standard​ deviation(s) the
the table is for the entire problem.

Answer 1

A.) - 0.2992

B.) Q1 = 36.75

Q2 = 38.45

Q3 = 41

C.) IQR = 4.25

D.) LOWER FENCE = 30.375

UPPER FENCE = 47.375

Yes, 49.3

Explanation:

Given the data:

Arranged data in ascending order :

31.5, 34.2, 34.7, 35.6, 36.0, 36.2, 37.3, 37.6, 37.8, 38.1, 38.2, 38.4, 38.5, 38.7, 39.5, 39.6, 40.1, 40.6, 41.4, 41.7, 42.2, 42.5, 43.4, 49.3

Using calculator to save computation time :

Population mean (μ) = 38.88

Standard deviation (s) = 3.61

A.) The zscore for individual who obtained 37.8 miles per gallon :

Standardized score formula :

Z = (Score(x) - mean) / standard deviation

Z = (37.8 - 38.88) / 3.61

Z = - 1.08 / 3.61

Z = - 0.29916

Z = - 0.2992

B) The quartile ;

Lower quartile (Q1) :

1/4(n +1)th term

n = sample size = 24

1/4(24 + 1)

= 1/4(25) = 6.25th term

(6th + 7th) =(36.2 + 37.3) = 73.5/2 = 36.75

Upper quartile (Q3) :

3/4(24 +1) = 3/4(25) = 18.75th term

(18th + 19th) = (40.6 + 41.4) = 82/2 = 41

Median (Q2) :

1/2(24 +1) = 1/2(25) = 12.50th term

(12th + 13th) = (38.4 + 38.5) = 76.9/2 = 38.45

C.) interquartile range :

Q3 - Q1 = (41 - 36.75) = 4.25

D.) OUTLIER

LOWER : Q1 - 1.5(IQR) = 36.75 - 1.5(4.25) = 30.375 ; values less than 30.375

UPPER : Q3 + 1.5(IQR) = 41 + 1.5(4.25) = 47.375 ; values greater than. 47.375