Friday, March 20, 2009

Introduction to Statistics

Today in class we started our Statistics unit. We started the class going over some ideas (found on the first couple slides) to start thinking about why and how statistics is used. Then we got into vocabulary. The terms are important and can be found on the 6th slide. There are also other notes following this and we also have a few homework questions. Mr. K stressed that this unit can be difficult and it is IMPORTANT to stop him and ask questions as soon as something is unclear. We spent a lot of time on Measures of Central Tendency and Dispersion today.

Measures of Central Tendency: Mean, Median, and Mode:

Mean: The mean can be found by adding up all of the quantities given and dividing that sum by the number of quantities that were added. The equation for calculating the mean is:
Where "x bar" represents the mean,
"N" represents the total number of quantities (if you added five numbers together this N would equal 5,
X means the sum of all data
For ex. If you had the numbers 17 11 23 6 and 3.
To find the mean add up all the numbers:

Next divide the sum (60) by the number of quantities that were added.
The answer would be: 12

Median: The median is the middle number in a given set of numbers. If the total number of numbers is even then the median is found by adding the two middle numbers and dividing by two. For example. If you had the numbers 17 11 23 6 and 3
The median would be found by first sorting the numbers from smallest to biggest
3 6 11 17 23
Next you would find the number in the middle:
11 If the set of numbers was 3 6 11 17 23 and 30
You would need to take the two middle numbers and add them then divide by two.
The answer would be 14.

Mode: The mode is the number that occurs most often in a set of data. When there are two numbers that show up an equal number of times it is termed Bimodal Distribution. *NOTE: When used in class distribution refers to "a bunch of data".
For example: If you had the numbers 8 14 14 20 and 24
The mean would be 14.
If the numbers were 8 14 14 20 20 24
The answer would be 14 and 24
Click here for practice problems

Measures of Dispersion: Range and Standard Deviation:

Range: The range is the difference between the smallest and largest values in a data set. The only values that matter when calculating the range are the highest and lowest numbers!
For example if you had the numbers: 5 10 15 20 and 25
Locate your highest number: 25
lowest number: 5
And subtract: 20
Standard Deviation: In standard deviation all the numbers in a data set 'matter'. It is a measure that shows how the data is dispersed in reference to the mean.
The symbol for Standard Deviation is

Mr. K also went over in class how to use our calculators for some of the calculations we will be learning this unit.

Next Scribe is Daniel


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