# Confidence Interval Calculator

Confidence Interval Calculator

## What is the confidence interval?

The confidence interval is used to describe the range of values that are likely to represent the true population parameter. The width of the confidence interval is a measure of how reliable the statistic is.

A brick maker can make bricks of the appropriate size if he or she knows how to manufacture bricks and if he or she knows the right mass of bricks to

He has measured the average mass of a sample of 100 bricks. They are equal to 3 kg.

He has calculated the 95% confidence interval to be 2.85 kg to 3.15 kg.

It means that he can be 95% sure that the average mass of all the bricks he manufactures will lie between 2.85 kg and3.15 kg.

Sometimes, you just want to be 95% sure. You might want to be 99% certain, or maybe it is enough for you that the confidence interval is correct in 90% of cases.

In this situation, this percentage is called the confidence level.

## What is a Confidence Level?

95% confidence intervals are made up at a confidence level — for example, 95 percent.

The confidence level is a measure of how confident the researcher feels about the findings of the study.

Though, what does a 95 percent confidence level indicate?

If a confidence level is 95 percent, it means that if the same population was to be sampled on multiple occasions, and estimates of a parameter were made on each occasion, the resulting intervals w

## How to Use the Confidence Interval Calculator?

The procedure to use the confidence interval calculator is as follows:**Step 1:** Enter Sample size, standard deviation, and mean in the respective input field and select confidence level.**Step 2:** Now click the button “Calculate” to get the interval value result.**Step 3:** Finally, the confidence interval will be displayed.

### Common critical values Z

Beneath is a table with standard-essential values used for constructing two-sided confidence intervals for statistics with generally-distributed mistakes.

Two-sided Confidence level | Critical value (Z) |
---|---|

80% | 1.2816 |

90% | 1.6449 |

95% | 1.9600 |

97.5% | 2.0537 |

98% | 2.3263 |

99% | 3.0902 |

99.9% | 3.2905 |