Lecture8-1

Lecture8-1 - BUAD 310 Applied Business Statistics Quiz 2...

Info iconThis preview shows pages 1–12. Sign up to view the full content.

View Full Document Right Arrow Icon
BUAD 310 Applied Business Statistics Quiz 2 Review 3/1/10
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
CI for a Population Mean 2 A confidence interval for an unknown population mean has the form Margin of error is a multiple of the SD or SE of the sample mean. Recall that deviation. standard sample the is and deviation population is where s n s x SE n x SD ) ( ) ( error of margin x
Background image of page 2
CI for a Population Mean with Known σ 3 If sampled population has mean μ and known σ, a (1-α)100% confidence interval for μ is /2 xz n 1.645 1.960 2.576 Level 90% 95% 99% 2 / z E.g.,
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Effect of Confidence Level on CI Width 4 The higher the confidence level (1-α)100% (e.g., 99%>95%), the longer is the CI.
Background image of page 4
CI for a Population Mean with Unknown σ 5 If sampled population is normally distributed with mean and unknown σ, then a (1 - α)100% confidence interval for μ is /2 s xt n is the t point giving right-hand tail area of /2 under t curve having n – 1 degrees of freedom (df). t
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Effect of df on t Distribution 6 As the number of degrees of freedom (df) increases, spread of t distribution decreases and the t curve approaches the standard normal curve. df =
Background image of page 6
More Practice 7 A business magazine samples 90 individuals responsible for economic forecasting for regional banks. Suppose that the sample of 90 forecasts yields an average prediction of a 2.7% growth in real disposable income. Assume that the population standard deviation is 0.4%. Calculate a 95% confidence interval for the population mean forecast.   783 . 2 , 617 . 2 083 . 0 7 . 2 90 4 . 0 96 . 1 7 . 2 025 . n z x 246 take 9 . 245 05 . 0 4 . 0 96 . 1 4 . 0 96 . 1 05 . 0 0.05? to 0.083 from error of margin lower the we could How 2 n n n
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
More Practice 8 An airline needs an estimate of the average number of passengers on a newly scheduled flight. The mean of a sample of 30 days is found to be 112.0 and the sample standard deviation is 25. Find a 95% confidence interval for the true mean.   334 . 121 , 666 . 102 334 . 9 112 30 25 045 . 2 112 025 . n s t x 29 30 df n
Background image of page 8
More Practice 9 An airline has 4 ticket counter positions at a particular airport. In an attempt to reduce waiting lines for customers, the airline introduces the “snake system.” Under this system, all customers enter a single waiting line that winds back and forth in front of the counter. A customer who reaches the front of the line proceeds to the first free position. The manager measures the waiting time for a sample of 15 customers and finds the mean time of 5.043 minutes and standard deviation of 2.266. Calculate a 95% CI for the mean waiting time under the new system.   298 . 6 , 788 . 3 255 . 1 043 . 5 15 266 . 2 145 . 2 043 . 5 14 15 025 . n s t x df n How about a 90% CI?   073 . 6 , 013 . 4 030 . 1 043 . 5 15 266 . 2 761 . 1 043 . 5 050 . n s t x
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
CI for a Population Proportion 10 A confidence interval for an unknown population proportion p has the form Margin of error is a multiple of the SE of the sample proportion . p ˆ error of margin p ˆ
Background image of page 10
CI for a Population Proportion 11 A (1 - α)100% confidence interval for population proportion
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 12
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 65

Lecture8-1 - BUAD 310 Applied Business Statistics Quiz 2...

This preview shows document pages 1 - 12. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online