Chapter 6 stats review
XL
(1+c)/2 then look it up
XR
(1-c)/2 then look it up
A doctor wants to estimate the HDL cholesterol of all 20- to 29-year-old females. How many subjects are needed to estimate the HDL cholesterol within 33 points with 99% confidence assuming σ=12.5? Suppose the doctor would be content with 90% confidence. How does the decrease in confidence affect the sample size required?
(zc)(o/E) all ^2 and always round up by one whole complete number
Find the critical value z Subscript zc necessary to form a confidence interval at the level of confidence shown below. c=0.93
1-.93=.07 .07 x1/2=.035 invnorm(.035)= -1.81 but always positive so 1.81
sample mean
sum / 2 answer cannot be negative
A researcher wishes to estimate, with 99% confidence, the population proportion of adults who think the president of their country can control the price of gasoline. Her estimate must be accurate within 6% of the true proportion. a) No preliminary estimate is available. Find the minimum sample size needed. b) Find the minimum sample size needed, using a prior study that found that 47% of the respondents said they think their president can control the price of gasoline. c) Compare the results from parts (a) and (b). (a) The sample size required to obtain a 99% confidence interval for
a) .05x.05 (2.576zc / .06)^2 = 461 Always round your answer then round up by 1 b) p= .47 q= 1-p = .53 .47x.53( 2.576/ .06) ^2= 460 Always round your answer then round up by 1
margin of error
difference / 2 answer cannot be negative
In a survey of 1110 adults from country A, 144 said that they were not confident that the food they eat in country A is safe. The point estimate for p = .130 (Round to three decimal places as needed.) The point estimate for: .87
p= small number / big number q= 1-p
In a random sample of five microwave ovens, the mean repair cost was $85.00 and the standard deviation was $11.50. Assume the population is normally distributed and use a t-distribution to construct a 99% confidence interval for the population mean μ. What is the margin of error of μ? Interpret the results.
stat test 8
In a survey of 2348 adults, 735 say they believe in UFOs. Construct a %95% confidence interval for the population proportion of adults who believe in UFOs.
stat test A x= smaller number n=bigger number c-level= % With 95% confidence, it can be said that the population proportion of adults who believe in UFOs is between the endpoints of the given confidence interval.
Match the level of confidence, c=0.95, with its representation on the number line, given x=58.1σ=8.8, and n=80 the one with the line graph ----------------------
stats test 7
sampling error
x-m
