In a study of environmental lead exposure and IQ, the data was collect

trainart1

trainart1

Answered question

2021-11-30

In a study of environmental lead exposure and IQ, the data was collected from 148 children in Boston, Massachusetts. Their IQ score an age 10 approximately follow a normal distribution with a mean of 115.9 and standard deviation of 14.2. Suppose one child had an IQ of 74.
A) Calculate the lower fence for the IQ data, which is the lower limit value that the IQ score can be without being considered an outlier.
B) Then, calculate the probability of obtaining an IQ score value of 74 or less.

Answer & Explanation

Steven Arredondo

Steven Arredondo

Beginner2021-12-01Added 18 answers

Step 1
Denote X as the IQ scores. It is given that X is normally distributed, with mean μ=115.9 and standard deviation σ=14.2. It is assumed that a child has an IQ score of 74.
Step 2
A) Calculating the lower fence of IQ data:
The lower fence for the data is given by the formula:
Lower inner fence=Q1(1.5×IQR)
=Q1(1.5×(Q3Q1))
Lower inner fence=Q1(3×IQR)
=Q1(3×(Q3Q1))
[EXCEL formula for Q1=NORM.INV(0.25,115.9,14.2)
EXCEL formula for Q3=NORM.INV(0.75,115.9,14.2)]
Lower inner fence=106.32221.5×(125.4778106.3222)
=106.322228.7333
=77.5889
Lower outer fence=106.32223×(125.4778106.3222)
=106.322257.4665
=48.8557
Step 3
It is assumed that a child has an IQ score of 74. Therefore, lower fence of IQ data, which is the lower limit value that the IQ score can be without being considered an outlier is 48.8557.
Step 4
B) Calculating the probability that IQ score value is less than or equal to 74:
The probability that IQ score value is less than or equal to 74 is given below:
P(X74)=0.0016
[EXCEL formula for P(X74)=NORM.(0.25,115.9,14.2)]
Thus, the probability that IQ score value is less than or equal to 74 is 0.0016.
Step 5
Answer:
A) The lower fence of IQ data, which is the lower limit value that the IQ score can be without being considered an outlier is 48.8557.
B) The probability that IQ score value is less than or equal to 74 is 0.0016.

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