Introduction

  • Confidence Level

Definition: The confidence level is a measure of the uncertainty or precision associated with a statistical estimate. It represents the probability that a confidence interval, calculated from a set of data, contains the true value of the parameter being estimated.

Commonly Used Levels: Confidence levels are often expressed as percentages, and a 95% confidence level is one of the most commonly used. A 95% confidence level implies that if we were to take many samples and create a confidence interval from each sample, we would expect about 95% of those intervals to contain the true population parameter.

  • Standard Deviation:

Standard deviation is a measure of the amount of variation or dispersion in a set of values. It indicates how much individual data points differ from the mean (average) of the data set. A low standard deviation suggests that the data points tend to be close to the mean, while a high standard deviation indicates that the data points are spread out over a wider range.

In statistical analysis, researchers often work with confidence intervals (CI) to estimate the range in which a true parameter value lies. This conversion tool is designed to calculate the standard deviation from a confidence interval, specifically for data collected from two distinct groups. The article explains the variables involved and the step-by-step process of how the standard deviation is derived from the provided confidence interval information.

Variables Definitions

  1. Upper CI Limit: The upper limit of the confidence interval for the data collected in both groups.
  2. Lower CI Limit: The lower limit of the confidence interval for the data collected in both groups.
  3. CI Level: The confidence interval level is expressed as a decimal value (e.g., 0.95 for a 95% confidence interval).
  4. Participants in Group 1: The number of participants in the first group.
  5. Participants in Group 2: The number of participants in the second group.
  6. Standard Deviation (SD): The calculated standard deviation based on the provided confidence interval information.

Conversion Formula

The calculation involves the following steps:

  1. Calculate the Standard Error Wide (seWide):
    t-value
  2. Calculate Standard Error (SE):
    SE
  3. Calculate Standard Deviation (SD):
    SD

Formula Reference - Cochrane Handbook