Here are the IQ test scores of 31 seventh-grade girls in a Midwest school distri

Question

Here are the IQ test scores of 31 seventh-grade girls in a Midwest school district 114 100 104 89 102 90 114 114 103 106 108 132 120 132 11 126 116 119 86 72 111 103 73 112 108 103 97 96 112 111 93 (a) These 31 girls are an SRS of all seventh-grade girls in the school district. Suppose that the standard deviation of IQ scores in this population is known to be ? 14. we expect the distribution of IQ scores to be close to Normal. Make a stemplot of the distribution of these 31 scores (split the stems) to verify that there are no major departures from Normality. You have now checked the "simple conditions" to the extent possible. (Enter your answers from smallest to largest. Enter NONE in any unused answer blanks.) Stems Leaves 13 (b) Estimate the mean IQ score for all seventh-grade girls in the school district, using a 99% confidence interval. (Round your answers to two decimal places.) IQ points eBook

Explanation / Answer

Solution :

SRS <- c(114,100,104,89,102,90,114,114,103,106,108,132,120,132,111,126,116,119,86,72,111,103,73,112,108,103,97,96,112,111,93)
length(SRS)

stem(SRS)

b)

avg <- mean(SRS) # taking average of the population
sdd <- 14 # population standard deviation
n <- 31 # population size

## using 99% confidence intervel
error <- qnorm(0.99)*sdd/sqrt(n)

left <- avg- error
right <- avg + error

Ans : 99.86 to 111.55

##################################

Problem : 2

Solution

avg <- 25.5
sdd <- 8.8
n <- 670

error <- qnorm(0.90)*sdd/sqrt(n) # 90% confidence level
error
left <- avg- error
right <- avg + error

Margin of Error : 0.435

Ans : 25.06 to 25.93

################################

error <- qnorm(0.95)*sdd/sqrt(n) # 95% confidence level
error
left <- avg- error
right <- avg + error

Margin of Error : 0.559

Ans : 24.94 to 26.05

####################################3

error <- qnorm(0.99)*sdd/sqrt(n) # 99% confidence level
error
left <- avg- error
right <- avg + error

Margin of Error : 0.790

Ans : 24.70 to 26.29

Q2)

Ans : Increasing the confidence level causes the margin of error to increase.

Related Questions

Navigate

• Browse (All)
• Browse H
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.