Travel Time to School A random sample of 50 12th-grade students was asked how long it took to get to school. The sample mean was 16.2 minutes, and the sample standard deviation was 12.3 minutes. (Source: AMSTAT Census at School) a. Find a 95 % confidence interval for the population mean time it takes 12th-grade students to get to school. b. Would a 90 % confidence interval based on this sample data be wider or narrower than the 95 % confidence interval? Explain. Check your answer by constructing a 90 % confidence interval and comparing this width of the interval with the width of the 95 % confidence interval you found in part a.
Travel Time to School A random sample of 50 12th-grade students was asked how long it took to get to school. The sample mean was 16.2 minutes, and the sample standard deviation was 12.3 minutes. (Source: AMSTAT Census at School) a. Find a 95 % confidence interval for the population mean time it takes 12th-grade students to get to school. b. Would a 90 % confidence interval based on this sample data be wider or narrower than the 95 % confidence interval? Explain. Check your answer by constructing a 90 % confidence interval and comparing this width of the interval with the width of the 95 % confidence interval you found in part a.
Solution Summary: The author calculates the 95% confidence interval for the population mean for 12th-grade students to reach school, using the MINITAB software.
Travel Time to School A random sample of 50 12th-grade students was asked how long it took to get to school. The sample mean was
16.2
minutes, and the sample standard deviation was
12.3
minutes. (Source: AMSTAT Census at School)
a. Find a
95
%
confidence interval for the population mean time it takes 12th-grade students to get to school.
b. Would a
90
%
confidence interval based on this sample data be wider or narrower than the
95
%
confidence interval? Explain. Check your answer by constructing a
90
%
confidence interval and comparing this width of the interval with the width of the
95
%
confidence interval you found in part a.
Definition Definition Measure of central tendency that is the average of a given data set. The mean value is evaluated as the quotient of the sum of all observations by the sample size. The mean, in contrast to a median, is affected by extreme values. Very large or very small values can distract the mean from the center of the data. Arithmetic mean: The most common type of mean is the arithmetic mean. It is evaluated using the formula: μ = 1 N ∑ i = 1 N x i Other types of means are the geometric mean, logarithmic mean, and harmonic mean. Geometric mean: The nth root of the product of n observations from a data set is defined as the geometric mean of the set: G = x 1 x 2 ... x n n Logarithmic mean: The difference of the natural logarithms of the two numbers, divided by the difference between the numbers is the logarithmic mean of the two numbers. The logarithmic mean is used particularly in heat transfer and mass transfer. ln x 2 − ln x 1 x 2 − x 1 Harmonic mean: The inverse of the arithmetic mean of the inverses of all the numbers in a data set is the harmonic mean of the data. 1 1 x 1 + 1 x 2 + ...
Throughout, A, B, (An, n≥ 1), and (Bn, n≥ 1) are subsets of 2.
1. Show that
AAB (ANB) U (BA) = (AUB) (AB),
Α' Δ Β = Α Δ Β,
{A₁ U A2} A {B₁ U B2) C (A1 A B₁}U{A2 A B2).
16. Show that, if X and Y are independent random variables, such that E|X|< ∞,
and B is an arbitrary Borel set, then
EXI{Y B} = EX P(YE B).
Proposition 1.1 Suppose that X1, X2,... are random variables. The following
quantities are random variables:
(a) max{X1, X2) and min(X1, X2);
(b) sup, Xn and inf, Xn;
(c) lim sup∞ X
and lim inf∞ Xn-
(d) If Xn(w) converges for (almost) every w as n→ ∞, then lim-
random variable.
→ Xn is a
Chapter 9 Solutions
Pearson eText Introductory Statistics: Exploring the World Through Data -- Instant Access (Pearson+)
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