Summary  
This chapter explains how to calculate and interpret confidence intervals, set alpha values, and formulate null versus alternative hypotheses for statistical inference.

General domain of usage  
Ecological research

A confidence interval is a range of estimated values for an unknown parameter. To calculate it, a confidence level must be specified. The most common confidence level is 95%, although 90% and 99% confidence levels are also frequently used.

Definition

## What Does a 95% Confidence Level Mean?

A 95% confidence level means that in 95% of cases, the estimate will fall within the lower and upper bounds of the interval.

## Alpha Value

The confidence interval is typically equal to 1 minus alpha (1-a), where alpha represents the probability of a Type I error. Type I errors occur when we incorrectly reject a true null hypothesis.

## Null and Alternative Hypotheses

The null and alternative hypotheses are assumptions used in statistical tests to make judgments based on data. In hypothesis testing, these hypotheses are mutually exclusive statements. Typically, we either attempt to reject or fail to reject the null hypothesis.

In this section, we will work with penguin data. By the end of this section, we will be able to confidently state that, with a "**95% level of confidence, the mean penguin mass is...**".

What does a confidence interval represent in statistics?

What does the alpha value represent in statistics, and how does it relate to the confidence level?

Learn core statistical concepts used in data analysis with Python. The course covers descriptive statistics, including mean, median, mode, variance, and standard deviation, as well as sampling, probability distributions, the Central Limit Theorem, and outlier detection.

Confidence Interval

What Does a 95% Confidence Level Mean?

Alpha Value

Null and Alternative Hypotheses

1. What does a confidence interval represent in statistics?

2. What does the alpha value represent in statistics, and how does it relate to the confidence level?