•
This week
•
Tuesday 9/29: Lecture 9
•
Tuesday 9/29: HW 5 posted after Lecture 9 (
different from usual
)
•
HW 5 due Friday 10/2 at 9:30 AM (
different from usual
)
•
Lab 5 posted Friday 10/2 at 10 AM (
different from usual
)
•
No class
Thursday 10/1
•
Next week
•
Tuesday 10/6:
Midterm 1
(time = 2 hours)
•
Any
2 consecutive hours
between 7 AM --- 11 PM
•
Exam at CatCourses
•
Thursday 10/8: Lecture as usual
Plans about Midterm (10/6)

•
Coverage: Ch 1-3
•
50 questions = 40 multiple choice + 10 fill-in
•
The best way to prepare:
•
Review all the lecture slides
•
Pause & think questions in class
•
Re-do all the HW
•
Exam questions will be very similar to HW questions!
•
Next week’s Tuesday 10/6:
Midterm 1
•
You take exam at CatCourses
•
Any
2 consecutive hours
between 7 AM --- 11 PM
•
Not OK
:
9-10am and then 4-5pm (
must be 2 consecutive hours
)
•
Timer will keep running even leave if you leave CatCourses
Midterm
: Next week’s Tuesday 10/6

PSY 010:
Analysis of Psychological
Data
Lecture 9: Normal distribution basics
Keke Lai
9/29/2020

Today
•
Normal distribution
•
Use normal distribution to find probabilities
•
Reading: Ch 3

Review
•
Z-score:
•
Based on Central tendency & Variability
•
Provides a context for understanding X
•
Compare scores from
different data sets
•
Standard score vs Raw score
•
“z = 2” means “X is 2 standard deviations above the mean”
•
“X is 1 std dev unit below the mean” means “z= ”
•
Q: An exam has µ = 60 and σ = 20. My score is 80. How far is my score
from the mean?
•
A: It’s asking what my z-score is.

•
The std dev () is just a number
•
1.6 std dev units =
•
“
My Logic score is
1 std dev
above the mean
”
= “
Raw score is
7 pt
above the mean
”
= “
Z-score is 1
”
•
“
My Math score is
1/3 std dev
below the mean
”
= “
Math raw score is
2 pt
below the mean
”
= “
Z-score is -1/3
”

Pause and think•If X is 1.5 standard deviation units below the mean, what’s the Z-score for X?
(A) Z= 1.5(B) Z= 1.5 SD units (C) Z= 1.5(D) Z = 1.5 SD units

Pause and think•If X is 1.5 standard deviation units below the mean, what’s the Z-score for X?

•If I got 70 from an exam and I’m 1 standard deviation below the mean, what’s my Z-score? We know the mean=80 and SD=10 for all the exam scores.

From descriptive to inferential
stats
•
So far things have been all about
descriptive statistics
•
Central tendency
•
Variability
•
Symmetric vs skewed
•
We are given a data set. Then we
try to extract information from this
data set.
•
In practice, we almost never have
the data set of real interest
(population)
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