Two Types of Random Variables
Discrete Random Variable:
These random variables only take discrete values.
(e.g. number of heads out of two tosses of a fair coin
this random variable can only take values 0, 1, 2.)
STT 421
Continuous Random Variables:
Th
Examples
Suppose we toss a coin and observe the resulting face at the top.
Experiment: tossing the coin.
Sample points: Head (H) and Tail (T).
Sample space: S = cfw_H, T.
Events: cfw_H, cfw_T, cfw_H,T and (the empty set).
STT 421
Suppose we throw a di
STT 421
Census and Sample survey
Ashoke Kumar Sinha
This note is based on Chapter 3
3
Few terminologies
Types of study
Population is the complete set of all items that we
are interested in studying.
A sample is a subset of the population.
Study of a wh
GoBack
Histogram 1a: class width 2
Histogram 1a: class width
2
Histogram 1b: class width
1
Histogram 1c: class width
0.5
Histogram 1d: class width
0.1
The density function
0.14
0.12
Histogram 2a: class width
2
Histogram 2b: class width
1
Histogram
STT 421
Zscores and normal distribution
Ashoke Kumar Sinha
This note is based on Chapter 1.3 of the textbook.
How to compare apples with oranges?
How to standardize?
A college admissions committee is looking at
the files of two candidates, one with a to
Example: Exam data
STT 421: some examples
Note: 0 = Male, 1 =Female
2
Chart of Major
Chart of Gender
Count
15
10
5
Bar chart and
pie chart for
Majors
5
4
Count
Bar chart and
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20
6
3
2
1
0
0
Biol
0
1
Chem
Econ
Math
Major
Phys
PolSc
Psyc
What is Statistics?
Statistics  a word with 2 meanings
A subject, like mathematics or physics. Statistics is
the science of learning from data.
Plural form of statistic, a value we compute from
(sample) data.
STT 421
Ashoke Kumar Sinha
Wikipedia: Stat
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l. Fifty applicants interested in working for the Food Stamp pro
designed to measure their aptitude for social work. Below is
for the scores data
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the relative frequency histogram
a. (7 pts.) Find the
l. Fifty applicants interested in working for the Food Stamp program took examination
designed to measure their a I
ptitude for social work. Below is the relati've'freQuency histogram
for the scores data.  ' I _ '
a. (7 pts.) Find the missing height m
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variable Y with mean 5
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STT 421 Summer 2008 Exam #1
Instructor: Erkan Name
Name: \ASkruc 359 r S SE lUlllarL S
PID: .W
Instructions
Read each problem carefully. Show all your work. Credit will only be
awardedif your work is included. Problem 1. The following relative equency
Remember
Population is the complete set of all items that we
are interested in studying.
Parameters are the values we calculate from the
population data.
Population mean (for quantitative variables),
population proportion (categorical variables) etc.
ar
Goal
Students will be able to:
Construct a confidence interval for a proportion.
Interpret a confidence interval for a proportion.
Check conditions for the use of inference about a
population proportion
STT 421
Independence (or sample less than 10% of
Setup
Suppose we take a random sample of size n
from a population with mean and standard
deviation .
The sample mean will serve the purpose of
point estimator of population mean .
Goal: To construct a Clevel C.I. for .
However the procedure will dep
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