No. & Date Asked  Question 

# 31 :: 10/29/07

What is the Z score of a 98% confidence interval?. . .
Confidence Intervals,
Confidence Level 
# 58 :: 10/29/07

Why don't statisticians calculate 100% confidence intervals?. . .
Confidence Intervals,
Confidence Level 
# 128 :: 3/25/08

What is the value of z score required for a 70% confidence interval?. . .
ZScore,
,
Confidence Intervals 
# 151 :: 4/14/08

A random sample of 25 households finds that an average of 2.3 people reside in each house (the standard deviation is 0.35). With a 95% confidence lev. . .
TINV,
tstatistic,
tdistribution,
Confidence Intervals,
Standard Error of the Mean,
Margin of Error 
# 152 :: 4/14/08

If 350 respondents out of a random sample of 1,000 Americans reported that they did not trust their government, what is your estimation at a 99% confi. . .
Adjusted Wald,
Confidence Intervals 
# 160 :: 4/21/08

in a sample of 1000 tv vieweres 330 watched a particlar programme. find 99 pecent confidence limits for tv viewers who watched this programme. . .
Confidence Intervals,
Adjusted Wald 
# 162 :: 4/22/08

I am trying to do A/B testing onweb page displays. One is the test the other is the control.
Could you help me determine the formula for sample size . . .
Confidence Intervals,
Control Chart,
A/B Testing,
pchart 
# 163 :: 4/22/08

When calculating confidence interval estimates...how is the x and standard deviation calculated?. . .
Standard Deviation,
Confidence Intervals 
# 164 :: 4/23/08

how to calculate one sided 95% confidence limits for a proportion.could you provide a formula . . .
Adjusted Wald,
Confidence Intervals,
OneTailed Area 
# 209 :: 5/29/08

In 1992, the FAA conducted 86,991 preemployment drug tests on job applicants who were to be engaged in safety and security relatd jobs and found that. . .
Central Limit Theorem,
binomial,
Normal Approximation,
Confidence Intervals 
# 212 :: 6/1/08

How would I figure out a 90% and 95% confidence interval for the below informaion? What would be the formula? Can I figure this out in Excel or Mega. . .
tdistribution,
Confidence Intervals,
TINV,
Margin of Error 
# 214 :: 6/2/08

I am charged with sampling expense report submissions for accuracy. We get 8000 T&E claims, and want to sample a subset making inferences about the p. . .
1sample ttest,
Confidence Intervals,
Sample Size 
# 215 :: 6/3/08

Annual starting salaries for college graduates with degrees in business administration are generally expected to be between $30,000 and $45,000. Assum. . .
Standard Normal Curve,
Confidence Intervals,
Standard Deviation,
Normally Distributed 
# 247 :: 6/24/08

Jeff:
Can you possibly share the actual formula you are using in this application to produce the Adjusted Wald calculations?
Thanks. . .
Adjusted Wald,
ZScore,
Confidence Intervals 
# 263 :: 7/6/08

Determine the critical value Za/2 that corresponds to 94% level of confidence
Compute the 90% confidence interval about m if the sample size, n, is. . .
Critical Value,
Confidence Intervals,
Margin of Error 
# 278 :: 7/15/08

out of a random sample 167 students pass an exam out of the 300. how do you calculate an exact 99% confidence interval for the proportion of sudents w. . .
exact interval,
Confidence Intervals 
# 315 :: 8/5/08

An engineer in an automotive factory wishes to know what the tire pressure is on all cars leaving the factory. She measures the tire pressure on a sa. . .
Standard Error of the Mean,
Standard Deviation,
Confidence Intervals,
Critical Value,
tstatistic 
# 351 :: 8/17/08

As an experiment, a selfconfessed connoisseur of cheap popcorn carefully counted 773 kernels and put them in a popper. After popping, the unpopped ke. . .
Confidence Intervals 
# 357 :: 8/25/08

Biting an unpopped kernel of popcorn hurts! As an experiment, a selfconfessed connoisseur of cheap popcorn carefully counted 773 kernels and put them. . .
Confidence Intervals,
Normal Approximation to Binomial ,
Proportion 
# 362 :: 9/1/08

Popcorn kernels take between 100 and 200 seconds to pop. What sample size (number of kernels) would be needed to estimate the true mean seconds to pop. . .
Small Sample,
Sample Size,
Margin of Error,
Confidence Intervals 
# 364 :: 9/4/08

A sample of 20 pages was taken without replacement from the 1,591page phone directory Ameritech Pages Plus Yellow Pages. On each page, the mean area . . .
Margin of Error,
Confidence Intervals,
Sample Size 
# 369 :: 9/5/08

A random sample of 10 miniature Tootsie Rolls was taken from a bag. Each piece was weighed on very accurate scale. The results in grams were 3.087 3.. . .
Margin of Error,
Sample Size,
Confidence Intervals 
# 383 :: 9/15/08

Briefly describe the concept of a confidence interval and provide an example.. . .
Confidence Intervals 
# 391 :: 9/18/08

An engineer in an automotive factory wishes to know what the tire pressure is on all cars leaving the factory. She measures the tire pressure on a sa. . .
Standard Error of the Mean,
tstatistic,
Confidence Intervals,
Critical Value 
# 402 :: 9/21/08

How can I compute a onesided 97.5% confidence interval using SPSS for this ?
IN a cohort of 121 eyes treated with drug A, 3 eyes experience a drug . . .
SPSS,
Confidence Intervals,
1sided Interval 
# 403 :: 9/22/08

Based on information obtained from a sample of 54, a 98% confidence interval for the average profit level of regional banks is given by 67.4 million t. . .
Standard Deviation,
Margin of Error,
Critical Value,
Confidence Intervals,
Confidence Level 
# 451 :: 10/3/08

A sample of the math test scores of 35 fourthgraders has a mean of 82 with a standard deviation of 15.
Find the 95% confidence interval of the mean. . .
Confidence Intervals,
Confidence Level 
# 458 :: 10/5/08

In 1992, the FAA conducted 86,991 preemployment drug tests on job applicants who were to be engaged in safety and securityrelated jobs, and found th. . .
Confidence Intervals,
Normality Assumption 
# 470 :: 10/9/08

A telescope manufacturer wants its telescopes to have standard deviations in resolution to be significantly below 2 when focusing on objects 500 light. . .
ChiSquare Distribution,
Confidence Intervals,
Standard Deviation,
Variance 
# 471 :: 10/9/08

A central university has a student population of 60,000. The university is interested in determining what proportion of them is in favour of a new gra. . .
Margin of Error,
Confidence Intervals,
Sample Size 
# 485 :: 10/27/08

Assume that the heights of 5 year old boys are normally distribued with a mean of 100cm and a standard deviation of 60. What is the sampling distribut. . .
TINV,
Confidence Intervals,
Standard Error of the Mean,
Standard Deviation of the Mean 
# 487 :: 10/28/08

Find a confidence interval for the mean assuming that each sample is from a normal population. Mean = 127, s = 27, n = 16. Find the 90% Confidence Int. . .
TINV,
tdistribution,
Confidence Intervals 
# 497 :: 11/6/08

A random sample of n=64 children of working mothers showed that they were absent from school an average of 5.3 days per term, with a standard deviatio. . .
Confidence Intervals,
Confidence Level 
# 502 :: 11/7/08

Administrative staff based at a business school in the UK are advised to take a 15 minute break from their personal computer after working on it for 9. . .
Confidence Intervals,
TDIST,
ttest,
ZScore 
# 504 :: 11/9/08

Calculate the 95% confidence interval on the following GPA's from 30 randomly selected students.
0.979
0.891
0.962
0.858
0.909
0.936
0.963
0.9. . .
Confidence Intervals,
Margin of Error,
tstatistic 
# 505 :: 11/11/08

Calculate a 98% confidence interval for the following data 15.7,15.7,15.5,15.2,15.2,15.1,15.3.. . .
Confidence Intervals,
TINV,
Margin of Error,
tstatistic 
# 506 :: 11/12/08

Suppose you are planning a sample of employees to determine the monthly average # of vacation days. Standards set: Confidence level of 99% and an erro. . .
Sample Size,
Margin of Error,
Confidence Intervals 
# 507 :: 11/12/08

In a survey of 500, 60% responded positively to an value question.
Calculate a confidence level at 95% to get an interval estimate for proportion?. . .
Sample Size,
Confidence Intervals,
Proportion 
# 509 :: 11/13/08

A researcher expects the population proportion of the Cubs Fans in Chicago to be 80%. Error of less than 5% confident of an estimate to be made from a. . .
Confidence Intervals,
Sample Size,
Margin of Error 
# 511 :: 11/13/08

A machine produces 3 inch nails. A sample of 100 nails is selected, and it is found that 25 are shorter than 3 inches. Find the 95% confidence interv. . .
Proportion,
Confidence Intervals,
OneTailed Area 
# 520 :: 11/23/08

Your company asks you to compare a new advertising campaign and the old one. Sample data on the accounts as follows:
Old: 40, 28, 35, 38, 31, 42, 26,. . .
Confidence Intervals,
Median,
Mode,
mean,
tstatistic,
Standard Error of the Mean 
# 521 :: 11/24/08

The width of a confidence estimate for a proportion will be:
a. Narrower for a 99% confidence interval than for a 95% confidence interval.
b. Wider . . .
Confidence Level,
Confidence Intervals,
Proportion 
# 523 :: 11/24/08

Use the given degree of confidence and sample data to construct a confidence interval for the population mean x. Assume that the population has a norm. . .
Confidence Intervals,
TINV 
# 551 :: 12/12/08

Philadelphia is conducting a study on the characteristics of tourists who drive to Eagles football games. Previous studies indicate that approximately. . .
Sample Size,
Confidence Intervals,
Proportion 
# 557 :: 12/16/08

Find the margin or error for the 95% confidence interval used to estimate the population proportion. In a survey of 7100 TV viewers, 38% said they wa. . .
Confidence Intervals,
Margin of Error 
# 635 :: 2/22/09

Linemarking for parking bays shall be determined by the retroreflectivity performance of glass beads in the linemarking. The linemarking average level. . .
1sample ttest,
Confidence Intervals 
# 637 :: 2/22/09

Hi Jeff thanks for all your help so far, your answers have been great and very timely. It is great to be able have help from someone with great profes. . .
Adjusted Wald,
Confidence Intervals 
# 683 :: 4/18/09

A baseball fan would like to estimate the mean time it takes to complete a major league baseball game. He randomly selects 40 game lengths (times to c. . .
Confidence Intervals 
# 684 :: 4/18/09

Tax companies imply that the returns they prepare are perfect, but what proportion of returns from tax companies have mistakes? To answer this questio. . .
Confidence Intervals,
Confidence Interval around a Proportion 
# 703 :: 4/26/09

The following data is a random sample of 1st quiz scores from previous Research 342 classes.
9.5, 6.5, 4.25, 8.5, 7.5, 4.5, 4.25, 6, 7
mean = 6.44 . . .
Confidence Intervals 
# 735 :: 5/25/09

how does a confidence interval this relate to learning statistics
How do you think confidence intervals are useful in the realworld?. . .
Confidence Intervals 
# 775 :: 7/6/09

1.A state meat inspector in Iowa has been given the assignment of estimating the mean net weight of packages of ground chuck labeled “3 pounds.” Of c. . .
Confidence Intervals 
# 859 :: 3/18/10

1) Spinifex pigeons are one of the few bird species that inhabit the desert of Western Australia. The pigeons rely almost entirely on seeds for food. . . .
Confidence Intervals 
# 860 :: 3/30/10

Problem # 1:
Clothing for Runners: Your company sells exercise clothing and equipment on the internet. To design the clothing, you collect a data on. . .
Confidence Intervals,
Margin of Error 
# 868 :: 10/14/10

Suppose that a 90% confidence interval for a population mean μ is constructed from a sample, resulting in the interval from 120 to 150. What was. . .
Confidence Intervals,
Margin of Error 
# 893 :: 7/12/11

Elbow to fingertip length of men 99% confidence n=32, x 14.50,s= 0.70 what is the margin of error. . .
Margin of Error,
Confidence Intervals 
# 905 :: 12/3/11

create a 95% confidence interval for the value of the population mean using the following information: a sample mean of 55, a sample standard deviatio. . .
Confidence Intervals 
# 914 :: 12/6/11

create a 95% confidence interval for the value of the population mean, given that their are 64 observations and a sample mean of 49, with a sample sta. . .
1sample ttest,
Confidence Intervals 
# 915 :: 12/6/11

create a 95%confidence interval for the value of the population mean, given that their is a sample mean of 49 and a standard deviation of 3 but now fo. . .
1sample ttest,
Confidence Intervals 
# 944 :: 4/29/12

Mr. price Home analyzed the value of purchase made on credit by a sample of 25 credit card customers. The simple mean was found to be R170.08 with a s. . .
Confidence Intervals 
# 945 :: 4/29/12

In a survey of 1000 electors, 20% were found to favour party "stats".
1. Construct a 95% C.I for the percentagew in favour of party "stats".
2. What. . .
Confidence Intervals,
Sample Size 