From fb90a189e1807561909880d52c824060e13897a5 Mon Sep 17 00:00:00 2001 From: eggy Date: Mon, 28 Sep 2020 09:00:21 -0400 Subject: [PATCH] math: remove second stdev equation --- docs/mhf4u7.md | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/docs/mhf4u7.md b/docs/mhf4u7.md index 48d98c0..6f68aad 100644 --- a/docs/mhf4u7.md +++ b/docs/mhf4u7.md @@ -187,9 +187,6 @@ $$\sigma = \sqrt{\frac{\Sigma f_i (x_i - \bar{x})^2}{n}}$$ where $f_i$ is the fr For ungrouped data, assume $f_i = 1$. -Alternatively, the above equation can be arranged to form the following equation, which is better remembered as **the means of the squares minus the square of the mean**. - -$$\sigma = \sqrt{\frac{\Sigma f_i x_i^2}{n}} - \bar{x}^2$$ In a typical bell-shaped distribution: - 68% of data lie within 1 standard deviation of the mean ($\bar{x} ± \sigma$) @@ -212,6 +209,8 @@ When performing an operation with a constant value to a whole data set: ### Linear correlation and regression + + **Correlation does not imply causation**. ## Resources