Did you mean, "How do you calculate the 99.9 % confidence interval to a parameter using the mean and the standard deviation?" ?
The parameter is the population mean μ. Let xbar and s denote the sample mean and the sample standard deviation. The formula for a 99.9% confidence limit for μ is
xbar - 3.08 s / √n and
xbar + 3.08 s / √n
where xbar is the sample mean, n the sample size and s the sample standard deviation. 3.08 comes from a Normal probability table.
Confidence intervals may be calculated for any statistics, but the most common statistics for which CI's are computed are mean, proportion and standard deviation. I have include a link, which contains a worked out example for the confidence interval of a mean.
A confidence interval is calculated using three key elements: the sample mean, the standard deviation (or standard error) of the sample, and the critical value from the relevant statistical distribution (such as the z-score or t-score) corresponding to the desired confidence level. The formula combines these elements to estimate the range within which the true population parameter is expected to lie, given the sample data. This interval provides a measure of uncertainty around the sample estimate.
It goes up.
A wider confidence interval indicates greater uncertainty about the estimate, suggesting that the true parameter value could lie within a broader range. This often occurs with smaller sample sizes or higher variability in the data. In contrast, a narrow confidence interval reflects greater precision and confidence in the estimate, indicating that the true parameter is likely to be closer to the estimated value. Thus, the width of the confidence interval provides insight into the reliability of the estimate.
For a 90 percent confidence interval, the alpha (α) level is 0.10, which represents the total probability of making a Type I error. This means that there is a 10% chance that the true population parameter lies outside the interval. The confidence level of 90% indicates that if the same sampling procedure were repeated multiple times, approximately 90% of the constructed intervals would contain the true parameter.
No. For instance, when you calculate a 95% confidence interval for a parameter this should be taken to mean that, if you were to repeat the entire procedure of sampling from the population and calculating the confidence interval many times then the collection of confidence intervals would include the given parameter 95% of the time. And sometimes the confidence intervals would not include the given parameter.
The standard deviation is used in the numerator of the margin of error calculation. As the standard deviation increases, the margin of error increases; therefore the confidence interval width increases. So, the confidence interval gets wider.
Confidence intervals may be calculated for any statistics, but the most common statistics for which CI's are computed are mean, proportion and standard deviation. I have include a link, which contains a worked out example for the confidence interval of a mean.
no
To find the Lower Confidence Limit (LCL) for a statistical analysis, you typically calculate it using a formula that involves the sample mean, standard deviation, sample size, and the desired level of confidence. The LCL represents the lower boundary of the confidence interval within which the true population parameter is estimated to lie.
No, the confidence interval (CI) doesn't always contain the true population parameter. A 95% CI means that there is a 95% probability that the population parameter falls within the specified CI.
, the desired probabilistic level at which the obtained interval will contain the population parameter.
The increase in sample size will reduce the confidence interval. The increase in standard deviation will increase the confidence interval. The confidence interval is not based on a linear function so the overall effect will require some calculations based on the levels before and after these changes. It would depend on the relative rates at which the change in sample size and change in standard deviation occurred. If the sample size increased more quickly than then standard deviation, in some sense, then the size of the confidence interval would decrease. Conversely, if the standard deviation increased more quickly than the sample size, in some sense, then the size of the confidence interval would increase.
Confidence IntervalsConfidence interval (CI) is a parameter with a degree of confidence. Thus, 95 % CI means parameter with 95 % of confidence level. The most commonly used is 95 % confidence interval.Confidence intervals for means and proportions are calculated as follows:point estimate ± margin of error.
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Confidence intervals represent an interval that is likely, at some confidence level, to contain the true population parameter of interest. Confidence interval is always qualified by a particular confidence level, expressed as a percentage. The end points of the confidence interval can also be referred to as confidence limits.
It will make it wider.