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Sometimes, it's better to group the data into classes. For example:
THese are the number of customers at a restaurant during lunch hours.
20 students were asked how many pets they have. Here is the raw data of the results:
- the arithmetic average of a data set
0 1 0 3 2 0 2 1 1 0
1 1 2 3 0 1 0 2 1 1
the sum of all data values
the number of data values
- the middle value of an ordered data set
13+1
If n=13, then =7, so the median is the 7th value.
If n=14, then =7.5, so the median is the average of the 7th and 8th value.
- the most frequently occurring number in a data set
- the most frequently occurring data value
In frequency tables, the mean =
describe
a quality or characteristic. It can be divided into categories. (DUH!)
This is telling us that "6" appeared in the data 14 times, so to help find the sum, we multiply 6 by 14 and add it to the other total values.
1. Vote choice in an election
always have a numerical value.
2. Time taken in the shower
3. Number of KFC lunches
per week
4. Favorite candy
n+1
5. Killcount in Call of Duty
40+1
=
6. Cost of a new computer in
various stores
2
= 20.5
7. Brands of football shoes
2
So, the median is the average of the 20th and 21st data values. The 20th is 6, and the 21st is 6. So the median is 6.
data can be counted.
data must be
measured.
So, the mean =
=
This is why we usually take a , which is a collection of data about a small part of the population only. This is obviously easier, and if you take a big enough sample, can
give a good idea about the whole
population.
A is collecting data about every individual in an entire population. This is hard to do.
2
If there are data values, the median is the
th data value.
Quantitative variables can
be or .
14+1
2
is the art of solving problems by collecting and analyzing data.