PSY 230 Exam 1 Review

A researcher is exploring the effect of classroom environments on learning. Two identical PSY230 courses are being taught by the researcher. One is taught in a room with glass walls which allows students to see persons walking past, the other is in a similarly configured room with opaque walls. Students' learning is assessed at the end of the semester with a comprehensive examination. The independent variable in this scenario is the: _______.

classroom environment (type of wall)

Which of the following z scores reflects the raw score farthest from the sample mean?

-3.2

The mean of a z distribution has a value of _______.

0

The sum of the prediction errors in linear regression equals ______.

0

Approximately .13% of scores in a z distribution fall beyond a z score of 3.0. About what percent of scores would fall below a z score of -3.0?

0.13

Problem B: The midterm and final grades in a course are provided below. Given these data, calculate the slope of the regression line. Hint: The value is between 0.5 and 0.6

0.54

The scores on a psychological measure are normally distributed with a mean of 50 and a standard deviation of 8. Using this information, determine the percentage of scores above 70.

0.62

Question based on Problem B: What is the value of the correlation coefficient? (Round to two decimal places).Hint: The answer is between .65 and .75.

0.66

Question based on Problem A:What is the value of the correlation coefficient? (Round to two decimal places).Hint: The answer is between .65 and .75.

0.73

Problem B: The midterm and final grades in a course are provided below. Given these data, calculate the correlation coefficient. Hint: The value is between .70 and .75

0.74

The standard deviation of a z distribution has a value of _______.

1

Using the method of scientific rounding found in the textbook, round 10.34500 to two decimal places.

10.34

What is the upper real limit of a reported value of 10 lbs when the smallest unit of measurement of the scale is 1 pound?

10.5

Question based on Problem A: What is the sum of squares of X (SSX)? Hint: The value is between 12 and 13

12.88

Question based on Problem B: What is the value of the numerator in the equation? Hint: The answer is between 1208 and 1210.

1208.61

Given that a population is normally distributed with a mean of 100 and a standard deviation of 16, determine the raw score that divides the distribution such that 5% of the scores are above it. (Hint: z = 1.645).

126.32

Problem B: Below is a table of scores from Rottentomatoes.com concerning the films released as part of the Marvel Cinematic Universe. Your task is to calculate the correlation between the Tomatometer (Reviewer's) scores and the Audience scores. Most, but not all, of the summary information needed to calculate the correlation coefficient has been provided. Use the worksheet on the following pages to guide your calculations. Note: An Excel spreadsheet is provided in the homework folder for you to calculate the remaining values as you learned in the Excel 1 assignment in lab. What is the sum of the cross products (X * Y)? Hint: The value is between 162400 and 162500

162471

Question based on Problem B: What is the sum of squares of X (SSX)? Hint: The value is between 1640 and 1645

1643.22

According to the stem and leaf plot above, how many individuals had a score of exactly 85 on the examination?

2

In the next questions, you will be asked to calculate descriptive statistics for the following sample of scores: 32, 30, 23, 40, 26, 35, 29, 39, 37, 22, 23, 34, 20, 20, 23 What is the range of the sample data above?

20

Question based on Problem B: What is the sum of squares of Y (SSY)? Hint: The value is between 2015 and 2017

2015.30

Σ(x)^2 X: [1, 2, 3, 4, 5] Calculate the sum using the formula and data above.

225

What is the mode of the following sample? 32, 30, 23, 40, 26, 35, 29, 39, 37, 22, 23, 34, 20, 20, 23

23

A class interval contains 5 out of the 20 scores in the sample. The relative frequency for that class interval is:

25%

What is the median of the following sample data? 32, 30, 23, 40, 26, 35, 29, 39, 37, 22, 23, 34, 20, 20, 23

29

This question is based on Problem C (Undergraduate Research Posters) What is the sum of the squared difference scores? Hint: This value is between 30 and 35.

32

The scores on a psychological measure are normally distributed with a mean of 50 and a standard deviation of 8. Using this information, determine the percentage of scores between 46 and 54.

38.30

Given that a population is normally distributed with a mean of 100 and a standard deviation of 16, determine the percent of scores between the mean and a raw score of 120 (enter the response to two decimal places)

39.44

Given the following three groups in which N = 15, what is the value of n3? (In other words, how many values are in Group 3?) Group 1: [1,2,3,4,5,6] Group 2: [5,4,3,2,1] Group 3: [3,2,1,0]

4

The scores on a psychological measure are normally distributed with a mean of 50 and a standard deviation of 8. Using this information, determine the percentage of scores below 36.

4.01

Problem B: The midterm and final grades in a course are provided below. Given these data, calculate the Y-axis intercept. Hint: The value is between 40 and 45

40.31

You are preparing a grouped frequency distribution using the techniques in Chapter 3. The values range from 50 to 98. You intend to group the data into approximately 10 class intervals. The interval width (i) for your class intervals should be:

5

Question based on Problem A: What is the sum of squares of Y (SSY)? Hint: The value is between 5 and 6

5.88

You are preparing a grouped frequency distribution using the techniques in Chapter 3. The data range from 52 to 97. The interval width (i) is 5. The lower apparent limit of the lowest class interval should be:

50

Using the method of scientific rounding found in the textbook, round 51.25500 to two decimal places.

51.26

Using the method of scientific rounding found in the textbook, round 54.2554 to two decimal places.

54.26

Σx^2 X: [1, 2, 3, 4, 5] Calculate the sum using the formula and data above.

55

Problem A: Below are scores for eight students. The X scores reflect grades received on quizzes related to correlations. The Y scores represent the grade on the correlations section of Examination 1. Your task is to calculate the correlation between X and Y. What is the sum of the cross products (X * Y)? Hint: The value is between 560 and 570

567

Question based on Problem A:What is the value of the numerator in the equation? Hint: The answer is between 6 and 7.

6.38

The value for the cumulative frequency for a class interval is 15. There are 25 scores in the sample. What is the cumulative percent?

60%

The scores on a psychological scale are normally distributed with a mean of 30 and a standard deviation of 10. If you administered this scale to 1200 individuals, how many would you expect to have scores between 24 and 38? Round down to the nearest whole number.

617

Approximately ______ percent of the values under a normal curve fall within 1 SD (standard deviation) of the mean.

68

The sum of squares isn't used as a descriptive statistic. In this homework, we're using it as a step in calculating the standard deviation. What is the sum of squares calculated for the following sample data (round to two decimal places)? 32, 30, 23, 40, 26, 35, 29, 39, 37, 22, 23, 34, 20, 20, 23

683.73

Σ(2x+1) X: [5, 4, 7, 9, 2, 6] Calculate the sum using the formula and data above.

72

A standard deviation of 10 values is 8.19. You add 5 points to each score in the sample. The standard deviation for the new sample is: ______________.

8.19

Jamie is taking a course in which components, for example, exams, have different weights contributing to the final grade. Given the averages and weights below, what is Jamie's overall grade? Round to two decimal places, if necessary, and omit the percent sign when entering your answer into Bb Learn.

82.30

Problem A: You're interested in seeing a new movie has just arrived in theaters. There is a linear relationship between audience and critic's scores for similar movies. If the critic's scores have an average of 84, what do you predict the audience score will be if the slope of the regression line is 0.7355 and the Y-axis intercept is 20.5633? Hint: The answer will be between 82 and 83.

82.35

Using the grouped frequency distribution above, calculate the percentile rank for a raw score of 87 (round to two decimal places).

82.50

Using the grouped frequency distribution above, calculate the percentile point for P70.

83.39

Problem B: The midterm and final grades in a course are provided below. Given these data, estimate the score on the final examination based on a midterm score of 83. Hint: The value is between 84 and 86

85.28

Given that a population is normally distributed with a mean of 100 and a standard deviation of 16, determine the percentile rank of a score of 120 (round to the nearest whole number).

89

What is the lower real limit of a reported value of 10 lbs when the smallest unit of measurement of the scale is 2 pounds?

9

You wish to calculate correlation between two variables. One is measured on the ratio scale, the other on the ordinal scale. Which of the following approaches should be used?

Spearman rank order correlation

This type of variable theoretically can have an infinite number of values between adjacent units on the scale.

Continuous

Transforming raw scores into z scores changes the shape of the distribution.

False

_______________ statistics are concerned with techniques that are used to describe or characterize the obtained data.

Descriptive

You calculate the equation for a least-squares regression line using values of X that range from 0 to 100. Based on this information, is the following statement true or false?It is permissible to use the least-squares equation to estimate Y based on a value of X equal to 150.

False

Observational studies can be used to determine causality.

False

Later in the course, we will make inferences about populations based on sample data. This one of the most frequent uses of statistics. This group of statistical methods are called ________________ statistics.

Inferential

The Celsius scale of temperature is an example of a variable measured on the ________________ scale.

Interval

This scale has equal intervals between adjacent units but does not have an absolute zero.

Interval

You are enjoying a relaxing hike when the answer to a problem you have been struggling with for days and had put aside suddenly revealed itself. This method of knowing is called the_____________.

Method of Intuition

This method of knowing uses reason alone to arrive at knowledge, often using syllogisms in which a major premise and a minor premise are followed by a conclusion. For example:All participants in the study were at least 18 years old.Andy was a participant in the study.Andy is at least 18 years old. This method of knowing is called _____________.

Method of Rationalism

This scale has categories for units.

Nominal

The question is based on Problem C (Undergraduate Research Posters) What type of correlation coefficient did you calculate?

Spearman

Which of the following is not a property of the mean?

Of the measures of central tendency, the mean is the most sensitive to sampling variation.

The values on this scale represent rank ordering.

Ordinal

This type of research is conducted on samples in an effort to estimate the level of one or more population characteristics.

Parameter estimation research

_________________ is a measure of the extent to which paired scores occupy the same or opposite positions in their own distributions.

Pearson r

The book lists two important benefits of the use of random sampling. They include...

Random sampling allows the laws of probability to be applied to our data. Random sampling helps achieve a sample that is representative of the population.

This scale has equal intervals between adjacent units and does have an absolute zero.

Ratio

Which of the following best describes the effect of restricting the range of either the X or Y variable when calculating a correlation?

Restricting the range will lower the correlation coefficient.

This method of knowing uses both reasoning and intuition but relies on objective assessments. Hypothesis testing is an essential step in the use of this method. This method of knowing is called:

Scientific Method

In the formula below, which operation would be performed first? (X + Y) * 3 - 1/2

The operation enclosed in parentheses

A researcher is interested in the effects of sleep on performance on scores on an examination in basic statistics. 100 students who completed the PSY 230 course during the previous semester were randomly assigned either to a group receiving 8 hours of sleep or a group receiving 4 hours of sleep. All of students resided either in Dorm A or Dorm B. Following the night of either 8 or 4 hours of sleep, participants completed a 100 item statistics exam. An independent-samples t test was used to determine whether there was a difference on examination scores between the two groups. The dependent variable in this scenario is:

The score on the statistics examination.

You create a histogram of 50 raw scores. You convert the raw scores to their z-score equivalents and create a new histogram. How will the shape of the two distributions differ?

The shape of the distributions will be the same. There will not be a difference in their shapes.

A researcher is interested in the effects of sleep on performance on scores on an examination in basic statistics. 100 students who completed the PSY 230 course during the previous semester were randomly assigned either to a group receiving 8 hours of sleep or a group receiving 4 hours of sleep. All of students resided either in Dorm A or Dorm B. Following the night of either 8 or 4 hours of sleep, participants completed a 100 item statistics exam. An independent-samples t test was used to determine whether there was a difference on examination scores between the two groups. The independent variable in this scenario is:

The sleep group (8 hour or 4 hour) to which the participant was assigned.

In statistical notation, N stands for ________________.

The total number of subjects or scores

For any linear relationship, there is only one line that will minimize the total prediction error according to the least-squares criterion.

True

True experiments, which include manipulation of the independent variable, measurement of the dependent variable, and random sampling, can be used to determine causality.

True

X minus mu would give you ____________.

a deviation score for population data

A statistic calculated on population data is known as __________________________.

a parameter

Given a set of N scores, dividing the sum of the scores by N would give you the ___________.

arithmetic mean

The textbook uses the abbreviation __ _ to denote the slope of the line for minimizing errors in predicting Y .

b y

Frequency distributions of nominal or ordinal data are customarily plotted using a _______.

bar graph

One descriptor of the following dataset would be that it is ______________. [1,1,2,3,4,5,5]

bimodal

The ____________ tells you how far away the raw score is from the mean.

deviation score

When calculating the sample standard deviation we ________________ to make it a more accurate estimate of the population standard deviation.

divide SS by N - 1 rather than N

A relationship between two variables that is best described by a straight line is called a _____________ relationship.

linear

A correlation coefficient expresses the ___________ and _________ of a relationship between two variables. (Remember to select two from the list).

magnitude direction

The ____________ is defined as the scale value below which 50% of the scores fall.

median

The least-squares regression line is the prediction line that ________ according to the least-squares criterion.

minimizes the total error of prediction

As the values of variable X go up, the values of variable Y go down. This is an example of a __________ relationship.

negative

When a curve is __________, most of the scores occur at the higher values of the X axis and the curve tails off towards the lower end.

negatively skewed

The real limits of a continuous variable are those values that are above and below the recorded value by _____ of the smallest measuring unit of the scale.

one-half

The _______________ is the percentage of scores with values lower than the score in question.

percentile rank of a score

The vertical distance between an observation on a scatter plot and the least-squares regression line represents ____________.

prediction error

The proportion of the variability of Y that is accounted for by X is calculated by:

r 2

________________ is a topic that considers the relationship between two or more variables for the purpose of prediction.

regression

A researcher is exploring the effect of classroom environments on learning. Two identical PSY230 courses are being taught by the researcher. One is taught in a room with glass walls which allows students to see persons walking past, the other is in a similarly configured room with opaque walls. Students' learning is assessed at the end of the semester with a comprehensive examination. The dependent variable in this scenario is the: _______.

score on the comprehensive examination

A measure of a line's rate of change is its ____________.

slope

The square root of the variance will give you the __________.

standard deviation

Much like a standard deviation quantifies the average deviation of scores around the mean, the _________________________ provides a measure of the average deviation of the prediction errors around the regression line.

standard error of estimate

One way to differentiate a bar graph from a histogram is that ____________________.

the bars touch on a histogram

In this chapter, the abbreviation i denotes ___________. (Chapter 3, pg. 51)

the interval width

An italicized X with a bar over it is referred to as " X -bar" and denotes _________________________.

the mean of the variable X

A cumulative frequency distribution indicates _____________________________________.

the number of scores that fall below the upper real limits of each interval

A cumulative percentage distribution indicates _____________________________________.

the percentage of scores that fall below the upper real limits of each interval

A relative frequency distribution indicates _____________________________________.

the proportion of the total number of scores that occurs in each interval

While the book covers the calculation of the Pearson r and Spearman rank order correlations, there are other types of correlations, too (e.g., the biserial and phi coefficients). The two most important considerations in selecting the proper correlation method are _____________ and _________________.

the shape of the relationship between the two variables the scale(s) of measurement for the variables

It is standard practice to carry all intermediate calculations to _________ decimal place(s) further than will be reported in the final answer.

two or more

The goal of a simple linear regression is to predict (estimate) the ______________________.

value of Y based on a value of X

Height, weight, age, reaction time, and drug dose are all examples of ________________________.

variables

The range divided by the number of class intervals in a planned frequency distribution will give you the _____________.

width of the class interval

When creating a scatterplot to illustrate a linear regression, the variable to be predicted should be placed on the ____ axis.

y