Psychological Statistics

Psychological Statistics

PSYC 260-01 and PSYC 260-02, Fall 2024
Lab Assignment #2:
Due: Upload work into Canvas by 9/25/24
Name or ID: Section:
The lab assignment will assess the following learning outcomes:
● Students will know the main statistics people use to describe variability and that
help us understand the world.
● Students will learn how to calculate measures of variability and understand how
changes in scores within distributions impact the variance and standard
deviation. APA.

Psychological Statistics

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Lab Assignment Instructions:
There are three (3) activities below to be completed using the Jamovi software and two
(2) short answer questions. Type directly into this document and then upload the
completed document into Canvas by 9/25/24. Be sure to answer all of the questions.
Instructions for Jamovi:
● To download Jamovi, go to https://www.jamovi.org and follow the instructions. If you
have any issues, reach out to me or the TA.
● How to Input data into Jamovi:
○ Create variables by clicking on ‘Variables” at the top and typing the names
of each variable in the Description box below.
○ Click “Edit” just below “Variables” and pick “Continuous” for the variable.
○ Click on “Data” and enter data into the columns.
● How to ask for variance and standard deviation:
○ Once data is entered, go to “Descriptives” under the “Exploration” menu.
○ Drag the “Score” variable into the variable section.
○ In the output options, make sure to check “Variance” and “Standard
Deviation.”
PSYC 260 McGuire Lab #2 2
Activity 1 (7 points). Let’s use Jamoiv to consider a simple dataset of exam scores for a
group of students. Create the variable “Score.” Enter the data in Jamovi and calculate
the variance and standard deviation. Then, answer the seven (7) questions.
Example Data: Student Exam Scores

Psychological Statistics

1. What are the variance and the standard deviation of the exam scores for the
group of students? This will give you an understanding of how much the scores
deviate from the mean on average.
2. What is the distance between the lowest score and the highest score? What do
we call this statistic? How does it differ from the standard deviation?
Student ID Score
1 78
2 85
3 90
4 72
5 88
6 95
7 80
8 76
9 89
10 84
PSYC 260 McGuire Lab #2 3
3. Which student’s score is furthest from the average (mean) score? Comparing the
individual scores to the mean.
4. What percentage of the students have scores within one standard deviation from
the mean? This question helps to assess how closely clustered the scores are
around the mean.
5. How does the standard deviation change if Student 6’s score is adjusted to 85?
This explores the impact of changing one score on the spread of the data.
6. Are most of the students’ scores closer to the mean or spread out far from the
mean? This question encourages interpretation based on the calculated standard
deviation.
7. If a new student scored 91, how would this affect the variance and standard
deviation? Add a new data point and calculate the new values to see the effect of
this additional score.

Psychological Statistics

Activity 2 (7 points). Let’s practice using monthly temperatures. Create two variables
one called “Month” and the other called “Temperature” and enter the data below under
each column. Then, calculate the variance, standard deviation, and mean for
Temperature in Jamovi and answer the seven (7) questions.
Example 2: Monthly Temperatures
Month Temperature (°F)
January
53.6
February 59.0
March
64.4
PSYC 260 McGuire Lab #2 4
1. What are the variance and standard deviation in the monthly temperatures for the
year? This will give an idea of how much the monthly temperatures deviate from
the average (mean) temperature.
2. Which month has the temperature closest to the average (mean) temperature for
the year? You can determine this by comparing each month’s temperature to the
mean.
3. Which month’s temperature deviates the most from the average? Find the month
with the largest difference from the mean temperature.
4. How many months have temperatures within one standard deviation of the
mean? This will show how many months have temperatures that are relatively
close to the average.
April 71.6
May 77.0
June
86.0
July 89.6
August 87.8
September 82.4
October
75.2
November
64.4
December
57.2
PSYC 260 McGuire Lab #2 5
5. How does the temperature variance change if August’s temperature increases by
37.4°F? This explores the effect of changing a specific data point on the overall
variance.
6. How does the range (difference between highest and lowest temperatures)
compare to the standard deviation? This will help you compare different ways of
measuring the spread of data.
7. If a new month was added with a temperature of 68.0°F, how would that affect
the variance and standard deviation? Adding a new data point allows you to see
how the spread of the data changes.

Psychological Statistics

Activity 3 (7 points)
Let’s practice using hours of exercise per week. Create the variable “Exercise” and,
again, enter the data. Then, calculate the variance, standard deviation, and mean in
Jamovi and answer the seven (7) questions.
Example 3: Weekly Hours of Exercise
Person’s ID Hours of Exercise (per week)
1 2
2 4
3 3
4 6
5 5
6 4
PSYC 260 McGuire Lab #2 6
1. What are the variance and standard deviation in weekly hours of exercise
among the group? This will show how spread out the exercise hours are
from the average number of hours.
2. Which person’s exercise hours deviate the most from the mean? Find out
who exercises the most or least compared to the average.
3. How many individuals have exercise hours within one standard deviation
of the mean? This question helps identify how many people have exercise
routines close to the group’s average.
4. How does the variance in weekly exercise hours compare to the difference
between the person who exercises the most and the person who exercises
the least? Compare variance with the range to see how each measures
data spread.
5. What is the percentage change in standard deviation if two individuals
decrease their exercise hours by 1 hour per week? This question tests how
small changes in exercise hours affect the spread of the data.
7 7
8 6
9 5
10 3
PSYC 260 McGuire Lab #2 7
6. Does the variance indicate that most individuals exercise consistently, or is
there a large difference in weekly hours of exercise? Use variance to
evaluate whether there is a wide difference in the number of hours people
exercise.
7. Are more people exercising within one standard deviation of the mean or
beyond it? Explore how many people have consistent exercise routines
compared to those who deviate from the group’s average.

Short Answers (2 points each)
1. Why should people report the standard deviation when they report the mean?
What information does it provide?
2. What is a real world example of how knowledge could be improved if people
regularly reported the standard deviation?