24 Apr Review course text and Moodle notes on the Normal Distribution Review this article on the Normal Distribution applied to business salary problems https://www.wallstreetmojo.com/normal-
Review course text and Moodle notes on the Normal Distribution
Review this article on the Normal Distribution applied to business salary problems https://www.wallstreetmojo.com/normal-distribution/
1) Select one continuous variable from the Student Generated Class Database. and name the variable,
StudentClassID:34
DegreeProgram:MBA
NumberOfDegrees:1
StatisticsPreception:Difficult
Sex:Female
NumberOfSiblings:4
CityPopulation:14493
NumberPriorStatCourses1
RateStatExperienceNovice
Do you have Children?No
Rank your comfort with using JASPDifficult
Rank of comfort with using ExcelVery Difficult
Are your left or right handed?Right
Rate your Math ComfortabilityProficient
Tags:
2) generate ONE piece of evidence (numerical summaries, tables, or charts) that supports or refutes that the variable you selected may potentially be normally distributed. 3) attach your generated evidence (numerical summaries, tables, and/or charts) to your post, and 4) discuss how you are justifying your claim of for or against normality be referencing your evidence. APA formatting is ALWAYS expected.
In your post, number your )responses (as above) so that it is clear what you are responding to
Continuous Distributions
Continous Probability Distributions: data values are measured and not counted | |||||
a probability DENSITY functions represented by mathematical functions | |||||
probabilities are calculated within ranges and not at specific values: P(a) is theoretically 0 but Excel does estimate the height of the probability density curve at 'a' | |||||
Shape | Range | Other | |||
Normal | Bell Shaped | negative infinity to infinity | mean = median | ||
Uniform | Rectangular & symmetric | a to b | mean = median | ||
Exponential | Skewed right | 0 to infinity | mean>median | ||
Normal Distribution Benefits | |||||
Many variables in business can be represented using a normal distribution | |||||
Used to approximate discrete probability distributions | |||||
can be completely defined (with it's mathematical function) with the mean and standard deviation | |||||
N(mean, standard deviation) |
normal
Calculating Normal Distribution Probabilities with Excel | ||||||||||
Excel transforms Xi data values to Z scores before calculating probabilties | ||||||||||
the standard normal distribution is used to determine the probablities | ||||||||||
Use NORMDIST in Excel | ||||||||||
Example | ||||||||||
You need | ||||||||||
Mean= | 10 | |||||||||
Standard Deviation = | 2 | |||||||||
STANDARDIZE | NORMDIST | 1-NORMDIST | ||||||||
Xi | Z-score | P(X<Xi) | P(X>Xi) | To find probability of ranges | ||||||
7 | -1.5 | 0.0668072013 | 0.9331927987 | P(Xa<X<Xb)=ABS(P(X<Xb)-P(X<Xa)) | ||||||
5 | -2.5 | 0.0062096653 | 0.9937903347 | |||||||
9 | -0.5 | 0.3085375387 | 0.6914624613 | Probability of age between 8 and 12 ? | ||||||
0.6826894921 |
=NORMDIST(Xi, mean, s, False)
=STANDARDIZE(Xi, mean, s)
problem samples
Calculating data values of a normal distribution when the corresponding Z score or probabilities are given | ||||||||||||||||
WHat is the X value associated with Z-Score = 1.5? | ||||||||||||||||
You Need | 73.75 | |||||||||||||||
Mean= | 70 | |||||||||||||||
STandard Deviation = | 2.5 | |||||||||||||||
What is the X value for the distribution where p = .35 for values less than X? | ||||||||||||||||
69.036698834 | ||||||||||||||||
What is the Z-score value for the distribution where p = .35 for values less than Z? | ||||||||||||||||
-0.3853204664 |
=NORMINV(p, mean, s)
=NORMSINV(p)
=mean + Z(s)
normality
Is the Data distribution approximately normal? | ||||||||||||||||||
check the histogram | ||||||||||||||||||
examine the descriptive statistics | ||||||||||||||||||
use a normality plot | ||||||||||||||||||
Plot A | Plot B | |||||||||||||||||
Mean and median should be near equal | bell-shaped histogram | |||||||||||||||||
Dots are close to line | ||||||||||||||||||
Suggests the distribution is approximately normal in shape |
Empirical Rule
Need a bell-shaped distribution to use the Empirical Rule | |||||||||||||||
Age | |||||||||||||||
80 | Age Desciptive Statistics | Approximately: | |||||||||||||
91 | 68% of data values are within 1 standard deviation of the mean | ||||||||||||||
77 | Mean | 79 | |||||||||||||
85 | Standard Deviation | 9.5694384163 | 95% of data values are within 2 standard deviation of the mean | ||||||||||||
71 | |||||||||||||||
89 | 99.7% of data values are within 3 standard deviations of the mean | ||||||||||||||
82 | |||||||||||||||
79 | |||||||||||||||
74 | |||||||||||||||
68 | Question1: Approximately what percent of the age data is within 1 standard deviation unit of the mean? | ||||||||||||||
103 | According to the Empirical Rule, approximately 68% of the age | ||||||||||||||
92 | data is within 1 standard deviation above and below the mean | ||||||||||||||
85 | |||||||||||||||
81 | Question2: Within what interval are approximately 68% of the age data values? (Hint: need standard deviation of the distirbution) | ||||||||||||||
82 | According to the Empirical Rule | ||||||||||||||
64 | lower bound | 69.5352344046 | |||||||||||||
81 | upper bound | 88.6741112372 | |||||||||||||
84 | |||||||||||||||
100 | |||||||||||||||
86 | |||||||||||||||
83 | |||||||||||||||
67 | |||||||||||||||
84 | |||||||||||||||
78 | |||||||||||||||
63 | |||||||||||||||
70 | |||||||||||||||
85 | |||||||||||||||
99 | |||||||||||||||
93 | |||||||||||||||
79 | |||||||||||||||
88 | |||||||||||||||
69 | |||||||||||||||
86 | |||||||||||||||
103 | |||||||||||||||
85 | |||||||||||||||
73 | |||||||||||||||
61 | |||||||||||||||
71 | |||||||||||||||
89 | |||||||||||||||
98 | |||||||||||||||
71 | |||||||||||||||
81 | |||||||||||||||
83 | |||||||||||||||
81 | |||||||||||||||
69 | |||||||||||||||
65 | |||||||||||||||
77 | |||||||||||||||
82 | |||||||||||||||
80 | |||||||||||||||
78 | |||||||||||||||
60 | |||||||||||||||
71 | |||||||||||||||
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73 | |||||||||||||||
86 | |||||||||||||||
84 | |||||||||||||||
79 | |||||||||||||||
77 | |||||||||||||||
85 | |||||||||||||||
72 | |||||||||||||||
83 | |||||||||||||||
89 | |||||||||||||||
85 | |||||||||||||||
91 | |||||||||||||||
73 | |||||||||||||||
76 | |||||||||||||||
87 | |||||||||||||||
73 | |||||||||||||||
86 | |||||||||||||||
85 | |||||||||||||||
78 | |||||||||||||||
94 | |||||||||||||||
79 | |||||||||||||||
76 | |||||||||||||||
79 | |||||||||||||||
76 | |||||||||||||||
64 | |||||||||||||||
78 | |||||||||||||||
65 | |||||||||||||||
71 | |||||||||||||||
72 | |||||||||||||||
68 | |||||||||||||||
81 | |||||||||||||||
84 | |||||||||||||||
77 | |||||||||||||||
68 | |||||||||||||||
70 | |||||||||||||||
82 | |||||||||||||||
66 | |||||||||||||||
81 | |||||||||||||||
82 | |||||||||||||||
79 | |||||||||||||||
55 | |||||||||||||||
99 | |||||||||||||||
68 | |||||||||||||||
74 | |||||||||||||||
80 | |||||||||||||||
76 | |||||||||||||||
89 | |||||||||||||||
69 | |||||||||||||||
79 |
Generating data
Generate Normal distribution of data in Excel | |||||||
Mean | 10 | ||||||
Standard deviation | 2 | ||||||
11.5819814265 | Use Copy …Paste … Paste Special … Values | ||||||
8.3738684914 | To keep data from continuing to update due to the RAND() feature | ||||||
9.0864744902 | |||||||
9.2572957454 | |||||||
9.3909571118 | |||||||
13.7527527534 | |||||||
10.8007385469 | |||||||
4.0893192297 | |||||||
8.9700785395 | |||||||
9.2928090436 | |||||||
8.8604097223 | |||||||
6.4852175137 |
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1
Chapter 5 and 6 notes Discrete and Continuous Probability Distributions
Discrete Probability Distributions
2
Discrete Probability Distribution Learning Objectives • Distinguish bet
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