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### Course: Class 11>Unit 13

Lesson 1: Measures of central tendency: mean, median and mode

# Comparing means of distributions

Sal compares the means of two different distributions given as dot plots. Created by Sal Khan.

## Want to join the conversation?

• Why do you need to multiply to get the answer? Is that a choice?
• Jordan is right, it does take up less space to use multiplication and more space with addition
• It would help if you start the video by labeling the X-axis as "Number of fruit eaten per day" and the Y-axis as "# of people (freshman's or seniors)". That would've made ti easier to follow for me.
• Did you (Khan) mean to say the median is the middle number at ? It's hard to tell what you meant, because the mode is the same as the median: 3. But it seems odd to call the mode the middle number.
• Median is the middle number, and the mode is the most commonly occurring number. (Occurs the most in a data set) The mode can be the same as the median if the middle number is also the most commonly occurring number. Does this clear things up?
• 0 + 2.1 + 2.2 + 4.3 + 3.4 + 5 + 6 + 19 / 15
why over 15 not over 8? And also why do you need to put the 0 there if it is zero and will not really effect the amount for it will not increase or decrease the sum of all those numbers. So why does it have to be included?
• Listen to the video more closely, paying particular attention to what Sal is saying and the math that he is writing out. He's not writing a "2.1", he's writing "2x1", because he's saying "We have two data points at 1". Basically, he's using a short-hand notation.

And you don't have to add the zero, but you do have to count it, so that the denominator is correct.
• The median is the middle number and the mode is the number that occurs the most. You mixed them up.
• And at , it is also confusing!
• Sal is multiplying the value of the dots by how many dots there are of that value. For example, there are 5 dots with the value 3 (look at the bottom dot plot). The reason why he is dividing the equation by 16 is because there is a total of 16 dots on the dot plot. Hope this helps!
• A lot of time wasted on calculating the mean. The video could have been a lot shorter and clearer.
• What site is he using I want to use that help me ?