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	Data Pilot - Confidence interval
		The bootstrap method can be used to calculate confidence interval for the average from each sample for the given confidence level.
		If the lower line for the subsample has a confidence probability lower that the set value, then, due to small sample size, it is impossible to determine the confidence interval for the set confidence probability.
		In spite of the fact that 90% confidence intervals for “C Mag” and “M 49” intersect, there is a 98% probability that the “M49” average is higher than the “C Mag” average.
	www.colorpilot.com /datapilot_ex01.html (368 words)

	Estimations With Confidence
		In practice, a confidence interval is used to express the uncertainty in a quantity being estimated.
		While the confidence interval for the mean is applicable to any population even with discrete random variables, such as proportion, the other two confidence intervals required testing for normality in order to be valid.
		As an alternative to direct test of hypothesis for the Mean and the Variance one may use a two-sided or one-sided confidence interval to test a hypothesis with a two-sided or one sided alternative hypothesis, respectively.
	home.ubalt.edu /ntsbarsh/Business-stat/otherapplets/Esteem.htm (516 words)

	Confidence Interval (Site not responding. Last check: 2007-10-02)
		Confidence intervals make a reasoned statement about the true mean of a population based on a random sample.
		If the researcher were to take 100 random samples with a 95% confidence interval for each sample, then he or she expects that for 95 of the 100 samples (95%), the range of values produced by the confidence interval procedure will include the true mean of the population.
		The width of the confidence interval increases as the confidence level increases, since with a greater width one is more likely to have included the true mean.
	www.cvgs.k12.va.us /DIGSTATS/main/descriptv/d_confidence.htm (481 words)

	Sample Size Calculator
		For example, if you use a confidence interval of 4 and 47% percent of your sample picks an answer you can be "sure" that if you had asked the question of the entire relevant population between 43% (47-4) and 51% (47+4) would have picked that answer.
		When you put the confidence level and the confidence interval together, you can say that you are 95% sure that the true percentage of the population is between 43% and 51%.
		The confidence interval calculations assume you have a genuine random sample of the relevant population.
	www.surveysystem.com /sscalc.htm (727 words)

	1.3.5.2. Confidence Limits for the Mean
		Confidence limits for the mean (Snedecor and Cochran, 1989) are an interval estimate for the mean.
		Interval estimates are often desirable because the estimate of the mean varies from sample to sample.
		Confidence intervals for other location estimators such as the median or mid-mean tend to be mathematically difficult or intractable.
	www.itl.nist.gov /div898/handbook/eda/section3/eda352.htm (894 words)

	Arizona Rangelands: Inventory and Monitoring: Confidence Interval
		A large confidence interval suggests that the sample does not provide a precise representation of the population mean, whereas a narrow confidence interval demonstrates a greater degree of precision.
		All confidence intervals are expressed according to a particular probability (also referred to as level of confidence) that the interval correctly includes the population mean.
		Confidence intervals are used in statistical analysis to describe the probability that two sample means are from the same population, provided that the data sets exhibit a normal distribution.
	ag.arizona.edu /agnic/az/inventorymonitoring/confidence.html (305 words)

	Confidence Intervals (Site not responding. Last check: 2007-10-02)
		The larger the confidence interval the less power a study has to detect differences between treatment conditions in experiments or between groups of respondents in survey research.
		(c) the desired width of the confidence interval (e.g., the 95% confidence interval or the 99% confidence interval).
		In this set of notes confidence intervals are first theoretically defined in terms of the mean and standard deviation of a large number of samples of equal size from a known population.
	web.uccs.edu /lbecker/SPSS/confintervals.htm (1228 words)

	Washington State Department of Health - Assessment Guidelines: Confidence Intervals
		Confidence intervals provide a means of assessing and reporting the precision of a point estimate, such as a mortality or hospitalization rate or a frequency of reported behaviors.
		A confidence interval is a range of values that is normally used to describe the uncertainty around a point estimate of a quantity, for example, a mortality rate.
		Confidence intervals are calculated with a stated probability (say 95%), and we say that there is a 95% chance that the confidence interval covers the true value.
	www.doh.wa.gov /Data/Guidelines/ConfIntguide.htm (2698 words)

	Statistics Glossary - Confidence Intervals
		A confidence interval gives an estimated range of values which is likely to include an unknown population parameter, the estimated range being calculated from a given set of sample data.
		Confidence limits are the lower and upper boundaries / values of a confidence interval, that is, the values which define the range of a confidence interval.
		A confidence interval for the difference between two means specifies a range of values within which the difference between the means of the two populations may lie.
	www.cas.lancs.ac.uk /glossary_v1.1/confint.html (741 words)

	New Confidence Interval Applet ( 7-Aug-1996)
		Each interval is based on a sample of size 5 taken from a standard normal distribution (mean=0 and variance=1).
		Pick an alpha for which a large number of confidence intervals are to be calculated by sliding the arrow along the alpha scale.
		The first line of text allows you to see what intervals cover the true mean of 0 for the current set of 50 intervals as you change alpha.
	www.stat.sc.edu /~west/javahtml/ConfidenceInterval.html (299 words)

	CONFIDENCE INTERVAL FOR A POP. MEAN using T
		Find a 99% confidence interval to estimate the mean percentage of body fat in male gymnasts on college teams.
		This procedure is valid when the population of percentage of body fat of male gymnasts is normally distributed, and a random sample is selected from that population.
		The usual structure for presenting the solution to a confidence interval was followed.
	www.nku.edu /~statistics/Confidence_Interval_using_t.htm (281 words)

	Confidence Intervals
		A 95% confidence interval for the mean yield of corn from farms using integrated pest management is 142.7 to 153.9 bushels per acre.
		Similarly, a 90% confidence interval is an interval generated by a process that's right 90% of the time and a 99% confidence interval is an interval generated by a process that's right 99% of the time.
		Confidence intervals contain population values found to be consistent with the data.
	www.tufts.edu /~gdallal/ci.htm (1748 words)

	Confidence Intervals (Site not responding. Last check: 2007-10-02)
		Each interval is computed as: sample mean ± t x se, where t is the 1 - (alpha/2) quantile of a t distribution with n-1 degrees of freedom and se is the standard error (i.e, s/sqrt(n)).
		The lengths of the confidence intervals vary since they are based on randomly selected samples (from the same normal parent distribution).
		The confidence intervals enclosing the true population mean (denoted as a red vertical line) are drawn in blue, whereas the intervals not containing the population mean are drawn in yellow.
	www.stat.wvu.edu /SRS/Modules/CI/ci.html (264 words)

	Stats: Confidence intervals
		Generally when a confidence interval is very wide like this one, it is an indication of an inadequate sample size, an issue that the authors mention in the discussion section of this paper.
		The confidence interval for the difference in two proportions, however, is (-16.7% to -1.5%) which provides evidence that the two proportions differ.
		The Confidence Interval of a Proportion, Richard Lowry.
	www.childrens-mercy.org /stats/model/confidence.asp (2483 words)

	8. Confidence Intervals
		Confidence intervals are numerical intervals in which the population mean might lie.
		When a confidence interval based on a single sample is computed, this confidence interval might or might not contain the population mean.
		Confidence intervals for population proportions appear almost daily in newspapers, in magazine articles, and on radio and television broadcasts.
	www.csus.edu /indiv/j/jgehrman/courses/stat50/confints/8confintervals.htm (1471 words)

	Confidence Interval for Means Calculator
		This calculator will determine the confidence interval for a chosen confidence level given a study’s sample size and a mean and standard deviation response to a survey.
		There is some likelihood, called the confidence level, that the true population mean falls within a particular range, called the confidence interval, around the mean value you obtained from your sample.
		Confidence level is related to the level of significance (α).
	www.dimensionresearch.com /resources/calculators/conf_means.html (311 words)

	Statistics Glossary - confidence intervals
		Confidence intervals are usually calculated so that this percentage is 95%, but we can produce 90%, 99%, 99.9% (or whatever) confidence intervals for the unknown parameter.
		These intervals may be calculated by, for example, a producer who wishes to estimate his mean daily output; a medical researcher who wishes to estimate the mean response by patients to a new drug; etc.
		These intervals may be calculated by, for example, a producer who wishes to estimate the difference in mean daily output from two machines; a medical researcher who wishes to estimate the difference in mean response by patients who are receiving two different drugs; etc.
	www.stats.gla.ac.uk /steps/glossary/confidence_intervals.html (740 words)

	ED230A Interval Estimation
		A confidence interval for a parameter is an interval computed from sample data containing the true value of the parameter with a certain level of confidence.
		With a 95% confidence interval for a sample mean, 95% of all sample of the same size will contain the true population mean.
		In general, the greater the degree of confidence the wider the confidence interval must be.
	www.gseis.ucla.edu /courses/ed230a2/notes2/interval.html (685 words)

	Z Confidence Interval
		The level of confidence measures the probability that the unknown mean µ; will actually be in a given confidence interval.
		So if the level of confidence is 0.95 and 100 random samples of size n are gathered, then around 95% of the resulting confidence intervals should contain µ.
		Find a 90% confidence interval for the mean percentage body fat µ of all men aged 20 to 29.
	www.wku.edu /~david.neal/statistics/confint/zconfint.html (997 words)

	Evans Data Corporation \| Research \| Research Methodology (Site not responding. Last check: 2007-10-02)
		All surveys have a confidence level and confidence interval or margin of error built in which can be determined by mathematical formulas.
		Confidence intervals are determined by sample size (or number of people who actually completed the survey).
		Due to a rule of calculus, the confidence intervals of all populations having more than 300,000 have the same confidence interval depending on the sample size.
	www.evansdata.com /n2/methodology.shtml (1070 words)

	Global Oral Health - CAPP
		Confidence interval is the range within which the true size of effect (never exactly known) lies with a given degree of assurance.
		This is the interval which includes the true value in 95% of cases.
		A trial where each of the groups will receive each of the treatments, but in a randomised order: that is, they will start off in one arm of the trial, but will deliberately 'cross over' to the other arm(s) in turn.
	www.whocollab.od.mah.se /expl/glossary.html (1378 words)

	New View of Statistics: Confidence Limits (Site not responding. Last check: 2007-10-02)
		The confidence interval is the length of the line between the limits.
		If the confidence interval was 0.02 to 0.10, you'd be satisfied that the tests were really different statistically, and you'd then have to decide whether the better validity was worth the hassle.
		The observed effect and your belief are combined with weighting factors inversely proportional to the square of the widths of their confidence intervals.
	www.sportsci.org /resource/stats/generalize.html (3162 words)

	confidence level interval
		With a sample of 100 cases per group the 80% confidence interval is plus/minus some 9 points (11 to 29) while the 95% confidence interval is plus/minus some 13 points (7 to 34).
		A one-tailed confidence "interval" extends from minus infinity to some value above the observed effect, or from some value below the observed effect to plus infinity (the logic of the procedure may impose a limit other than infinity, such as 0 and 1 for proportions).
		For any given sample size, dispersion and confidence level, a one-tailed confidence "interval" is "narrower" than a two tailed interval in the sense that the distance from the observed effect to the computed boundary is smaller for the one-tailed interval (the one-tailed case is not really an interval, since it has only one boundary).
	www.power-analysis.com /precision_confidence_level.htm (460 words)

	Confidence Interval for Proportions Calculator
		This calculator will determine the confidence interval for a chosen confidence level given a study’s sample size and survey result.
		When you are interviewing a sample of respondents drawn from a population, the percentage value (proportion) you obtain at a certain question may be different from the percentage value you would obtain if all members of the population where interviewed (true population proportion).
		There is some likelihood, called the confidence level, that the true population percentage falls within a particular range, called the confidence interval, around the proportion value you obtained from your sample.
	www.dimensionresearch.com /resources/calculators/conf_prop.html (373 words)

	Quantile confidence interval
		As with all non-parametric confidence intervals, the exact confidence level is not always attainable but the level which is exact to the interval cons
		A presentation of medians and their confidence intervals is often more meaningful than the time honoured (abused) tradition of presenting means and standard deviations.
		eans and their confidence intervals in situations where a median with confidence interval would be more appropriate (e.g.
	www.statsdirect.com /help/nonparametric_methods/qci.htm (353 words)

	Confidence Intervals
		Choose a statistic (usually this is one of the parameter-estimators we use to give point-estimates for the population parameter in question) and compute its value from the observed sample data.
		The confidence interval (range of values) for the parameter under investigation is then given by:
		The level C confidence interval for the population proportion p will have margin of error at most m, if n is chosen to be:
	www.marin.cc.ca.us /~npsomas/Confidence_Intervals.htm (544 words)

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