# Course Updates for High School Statistics in July 2021

We are excited to share that we've made significant enhancements to our **High School Statistics** course. One consequence of adding this new content is that it may impact learners’ Mastery percentages.

When we add new content and remove old content, Mastery percentages often change because the **number of available skills changes**. For example, if you mastered 90 out of 100 skills in a course, and we added 10 new skills, your mastery skill count would then be 90 out of 110. This change would change your Mastery percentage from 90% to 82%.

With this specific course update, we expect that Mastery percentages will change by a maximum of **65%**. Most people will see a much smaller Mastery percentage change.

You can see exactly what content items we’ve added and removed below. Happy learning!

**Content Added**

*Articles*

*Exercises*

Develop probability distributions: Theoretical probabilities |

*Videos*

**Content Removed**

*Articles*

Comparing range and interquartile range (IQR) |

The idea of spread and standard deviation |

Calculating standard deviation step by step |

Two-way frequency tables |

Two-way relative frequency tables and associations |

Positive and negative associations in scatterplots |

Samples and surveys |

Observational studies and experiments |

Probability: the basics |

Theoretical and experimental probability: Coin flips and die rolls |

Expected value (basic) |

Binomial probability (basic) |

*Exercises*

Shape of distributions |

Mean, median, and mode |

Missing value given the mean |

Standard deviation of a population |

Create two-way relative frequency tables |

Constructing scatter plots |

Making appropriate scatter plots |

Positive and negative linear associations from scatter plots |

Describing trends in scatter plots |

Valid claims |

Making inferences from random samples |

Types of statistical studies |

Simple probability |

Experimental probability |

Making predictions with probability |

Comparing probabilities |

Probability models |

Adding probabilities |

Probabilities of compund events |

Independent probability |

Dependent probability |

The counting principle |

*Videos*

Shapes of distributions |

Mean, median, & mode example |

Missing value given the mean |

Impact on median & mean: removing an outlier |

Impact on median & mean: increasing an outlier |

Effects of shifting, adding, & removing a data point |

Measures of spread: range, variance & standard deviation |

Constructing a box plot |

Comparing distributions with dot plots (example problem) |

Interpreting a trend line |

Constructing a scatter plot |

Example of direction in scatterplots |

Reasonable samples |

Types of statistical studies |

Appropriate statistical study example |

Intro to theoretical probability |

Simple probability: yellow marble |

Simple probability: non-blue marble |

Experimental probability |

Theoretical and experimental probabilities |

Making predictions with probability |

Intuitive sense of probabilities |

Probability models example: frozen yogurt |

Free-throw probability |

Independent & dependent probability |

Dependent probability: coins |

Counting outcomes: flower pots |

Count outcomes using tree diagram |

Probability with counting outcomes |

Example: All the ways you can flip a coin |

Example: Combinatorics and probability |

Binomial probability example |

Generalizing k scores in n attempts |

Free throw binomial probability distribution |

Graphing basketball binomial distribution |