Answer:
(A) 1199.168
(B) 1503.372
(C) 159.17728
Step-by-step explanation:
(A) To determine the 30th percentile for the number of chocolate chips in the bag, we find the z-score for the 30th percentile.
Found using a z-table or z-calculator, the z-score for the 30th percentile is -0.524
The formula for finding X (the number of items in a given percentile) is:
X = M + Z(S.D.)
Where M is the mean, Z is the specific z-score of the sought percentile and S.D. is the standard deviation.
So for the 30th percentile,
X = 1261 + (-0.524)(118)
X = 1261 - 61.832 = 1199.168
(B) The number of chocolate chips that make up the middle 98% of chips in the bag is
X = 1261 + (2.054)(118)
X = 1261 + 242.372 = 1503.372
(C) For normal distributions, Interquartile range is Q3 - Q1, that is; 3rd quartile minus 1st quartile.
This is within 1.34896 standard deviations of the mean.
IQR = (1.34896)(118)
IQR = 159.17728
