Week 3 lecture_math_221_nov_2012

B. Heard
(These may not be copied, reproduced, or posted
in an online classroom without my permission.
Students may download one copy for personal use.)

 Data Collection
 Understand and distinguish between
 Sampling
 Census
 Experiments
 Simulations
 Etc.

 Descriptive & Inferential Statistics
 Know the difference
 Descriptive - This is a set of methods to describe
data that we have collected.
 Inferential - This is a set of methods used to
make a generalization, estimate, prediction or
decision.

 Knowthe difference between Qualitative and
Quantitative Data

 Types of Sampling
 Random
 Stratified
 Cluster
 Systematic
 Convenience

 Populations and Samples
 Parameters and Statistics

 Standard Deviation and Variance
 How to calculate and mathematical relationship.
 Variance is the Standard Deviation squared.
 Standard Deviation is the square root of the
Variance.
 For example if you are given the standard
deviation is “3” and asked what the variance
is, you would note it as “9” because 3^2 is 9.
 If you were given the variance as 4.7 and asked
for the standard deviation, you would note it as
“2.17” because √4.7 = 2.17

 Be able to get a regression equation.
 Example
 Data (4, 30), (4,35), (5,36), (6,42), (8,48)

 Be able to get a regression equation.
 Example
 Data (4, 30), (4,35), (5,36), (6,42), (8,48)

This would be written
as y = 3.982x + 16.70

 Use a multiple regression equation.
• “Plug and Chug” (Plug in the values and chug out
the answer)
• Example
y = -6.5 +12a + 5.1b where “a” is a vocabulary
score and “b” is a skills test score. y predicts
the person’s score on a job performance test.
Predict a job test score for a person who made a
50 as a vocabulary score and got a 7 as a skills
test .
y = -6.5 +12(50) + 5.1 (7)
y = 629.2

 Correlation Coefficients, also noted as “r”
• Range from -1 to +1
• .75 to 1 is strong
• .5 to .75 is moderate
• .25 to .5 is weak
• 0 to .25 is almost none, I would probably note it
is as “NO CORRELATION”
• + would be positive correlation, - would be
negative correlation
• For example, -0.58 would be moderate negative
correlation

 Be able to create a stem and leaf plot
 Use Minitab!

 Determine descriptive statistics.
• Mean, Median, Mode, Range, Variance, Standard
Deviation
 Use Minitab!

 Identify Class Width
 Identify Midpoint of certain classes
 Identify class boundaries
 Give the relative frequency
 Fishing Tournament Data below is an example

Number of Fish Frequency
0-7 9
8-15 15
16-23 12
24-31 3

 Class Width is 8

0-7 9
8-15 15
16-23 12
24-31 3

8-0 = 8, or you could have
said 15 – 7 = 8, or count
on your fingers,
0,1,2,3,4,5,6,7
(There are eight numbers,
don’t let it fool you)

 Midpoint of second class is 11.5

0-7 9
8+15 = 23
divided by 2 8-15 15
gives you 11.5 16-23 12
24-31 3

 What are the class boundaries of the third class?

15.5 and 23.5

0-7 9
8-15 15
Subtract .5 from 16-23 12
the lower to get 24-31 3
15.5 and add .5
to the upper to
get 23.5

 Give the relative frequency of all classes

Number of Fish Frequency Relative Frequency
0-7 9 9/39
8-15 15 15/39
16-23 12 12/39
24-31 3 3/39
Total of 39

Total your Frequency column, the total is your
denominator for your fractional relative frequencies.
You could also have noted these in decimal form.

 Come see me at the “Statcave”
 www.facebook.com/statcave
 You DO NOT have to be a Facebook person to
see these.
 If you are, become a fan.
 IT IS NOT REQUIRED TO BE ON FACEBOOK.
IT’S SOMETHING I DO FOR FUN.
 I often post helpful things there for fun and
you can look at old posts that may be
helpful.

Week 3 lecture_math_221_nov_2012

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