Stats Exam 1

How do the sample mean and population mean differ?

A population mean is the mean for a set of scores in an entire population, whereas the sample mean is the mean for a sample, or subset of scores from a population.

dependent variable

Is the variable that is believed to change in the presence of the independent variable. It is the "presumed effect".

independent variable

Is the variable that is manipulated in an experiment. This variable remains unchanged between conditions being observed in an experiment. It is the "presumed cause". The specific conditions of an IV are referred to as the levels of IV.

Frequency data are not always distributed in intervals. What types of data are not distributed in intervals?

Ungrouped data sets with only a few different scores, and qualitative or categorical variables.

Why is variance, as a measure of variability, preferred to the range, the IQR and the SIQR?

the variance is preferred because it includes all scores to estimate variability

sample statistic

A characteristic (usually number) that describes a sample if referred to as a sample statistic.

can a nominal variable be numeric? explain.

yes, a number is assigned to represent something or someone

biomodal distribution

is a distribution of scores where two scores occur most often or most frequently. a biomodal distribution has two modes.

scatter gram or scatter diagram or scatter plot

is a graphical display of discrete data points (x,y) used to summarize the relationship between two variables.

histogram

is a graphical display used to summarize the frequency of continuous data that are distributed in numeric intervals (grouped).

bar char or bar graph

is a graphical display used to summarize the frequency of discrete and categorical data that are distributed in whole units or classes.

stem-and-leaf display or stem-and-leaf plot

is a graphical display where each individual score from an original set of data is listed. the data are organized such that the common digits shared by all scores are listed to the left (in the stem), with the remaining digits for each score listed to the right (in the leaf).

standard deviation or root mean square deviation

is a measure of variability for the average distance that scores deviate from their mean. it is calculated by taking the square root of the variance

population standard deviation

is a measure of variability for the average distance that scores in a population deviate form their mean. it is calculated y taking the square root of the population variance

variance

is a measure of variability for the average squared distance that scores deviate from their mean

population variance

is a measured of variability for the average squared distance that scores in a population deviate from the mean. it is computed only when all scores in a given population are known.

sample variance

is a measured of variability for the average squared distance that scores in a sample deviate from the mean. it is computed when only a portion or sample of data is measured in a population

proportion

is a part or portion of all measured data. the sum of all proportions for a distribution of scores is 100.

random assignment

is a random procedure used to ensure that participants in a study have an equal chance of being assigned to a particular group or condition.

simple frequency distribution

is a summary display for (1) the frequency of each individual score or category (ungrouped data) in a distribution or (2) the frequency of scores falling within defined groups or intervals (grouped data) in a distribution

frequency distribution

is a summary display for a distribution of data organized or summarized in terms of how often a category, score, or range of scores occurs.

relative percent

is a summary display that distributes the percentage of scores occurring in each interval relative to all scores distributed.

quasi-independent variable

is a variable whose levels are not randomly assigned to participants (nonrandom). This variable differentiates the groups or conditions being compared in a quasi-experiment.

computational formula for variance or the raw scores method for variance

is a way to calculate the population variance and sample variance without needing to sum the squared difference of scores from their mean to compute the SS in the numerator

open interval or open class

is an interval with no defined upper or lower boundary.

biased estimator

is any sample statistic, such as a sample mean, obtained from a randomly selected sample that does not equal the value of its respective population parameter, such as a population mean, on average

unbiased estimator

is any sample statistic, such as a sample mean, obtained from a randomly selected sample that quals the value of its respective population parameter, such as a population mean, on average.

sample

is defined as a set of selected individuals, items, or data taken from a population of interest.

population

is defined as the set of all individuals, items, or day of interest. This is the group about which scientist will generalize.

stem

is located to the left of the vertical line in a stem-and-leaf display. A stem lists the first digit or digits for each number in each row.

semi-interquartile range (SIQR) or quartile deviation

is measure of half the distance between the cutoffs for the upper and lower quartiles of a distribution. the SIQR is computed by dividing the IQR in half

continuous variable

is measured along a continuum at any place beyond the decimal point. Continuous variables can be measured in whole until or fractional units.

discrete variable

is measured in whole units or categories that are not distributed along a continuum.

real range

is one more than the difference between the largest and smallest value in a data set.

sample size

is the number of individuals that constitute a subset of those selected from a larger population. the sample size is represented by a lowercase n.

coding

refers to the procedure of converting a nominal value to a numeric value.

Hilari and Northcott (2006) used a social support survey (SSS) to gauge how well supported individuals suffering from stroke-induced aphasia (a language disorder) felt more than one year following the stroke. They reported that "in terms of social support, the SSS scores were negatively skewed with a mean of 3.69, suggesting that participants felt overall well supported" (p.17). Based on their findings, what additional measure of central tendency would be appropriate to report with these data? Explain.

the median because these data are negatively skewed

How many scores are included in the computation of the range?

two scores; the largest and smallest score in a distribution

in an experiment, researchers measure two types of variables: independent and dependent variables. a) which variable is manipulated to create the groups? b) which variable is measured in each group?

a) independent variable is manipulated b) the dependent variable is measured

scales of measurement

Are rules of how the properties of numbers can change with different uses.

state whether each of the following describes a study measuring qualitative or quantitative data. a) a researcher distributed ion-ended questions to participants asking how they feel when they are in love. b) a research records the blood pressure of participants during a task meant to induce stress c) a psychologist interested in a drug addiction inject with an attention-inducing drug and then measures the rate of lever pressing. d) a witness to a crime gives a description of the suspect to police

a) qualitative b) quantitative c) quantitative d) qualitative

Wickham, Morris and Fritz (2000) wrote that,"Although there has been extensive interest in the influence of distinctiveness on memory for faces, measuring the distinctiveness of a face is problematic because distinctiveness is difficult to define" (pg. 99-100). What type of definition will researchers need to make for the term distinctiveness?

an operational definition

percentile ranks

are a cumulative percent summary. the ranks indicate the percentage of scores at or below a given value and must be summed from the smallest value.

grouped data

are a set of scores distributed into intervals, where the frequency of each score can fall into any given interval.

cumulative percents

are a summary display that distributes the sum of relative percents across a series of intervals. this summary is presented from the bottom up and is called a percentile rank.

outliers

are extreme scores that fall substantially above or below most of the scores in a particular data set.

ratio scales

are measurement where a set of values has a true zero and are equidistant.

ordinal scale

are measurement where values convey order or rank alone.

positively skewed distribution

is a distribution of scores where a few outliers are substantially larger (toward the right tail in a graph) than most other scores

negatively skewed distribution

is a distribution of scores where a few outliers are substantially smaller (toward the left tail in a graph) than most other scores

skewed distribution

is a distribution of scores that includes outliers or scores that fall substantially above or below most other scores in a data set

nonmodal (rectangular) distribution

is a distribution of scores where all scores occur at the same frequency. a nonmetal distribution has no mode

multimodal distribution

is a distribution of scores where more than two scores occur most often or most frequently. a multimodal distribution has more than two modes.

modal distribution

is a distribution of scores where one or more scores occur most often or most frequently

unimodal distribution

is a distribution of scores where one score occurs most often or most frequently. a unimodal distribution has one mode

ogive

is a dot-and-line graph used to summarize the cumulative percent of continuous data at the upper boundary if each interval.

frequency polygon

is a dot-and-line graph used to summarize the frequency or continuous data at the midpoint of each interval.

A student computes a variance of 9. Will the standard deviation differ if 9 is the value for a population versus a sample variance? Explain.

no in both cases the standard deviation is the square root the variance. hence, the population and the sample standard deviation will be square root of 9=3.0

rank the scales of measurement in order from least informative to most informative.

nominal, ordinal, interval, and ratio

by definition, how is a sample related to a population?

population is all individuals and sample is just a set of selected individuals

data points or bivariate plots

are the x- and y-coordinates for each plot in a scatter gram.

equidistant scales

are those values whose intervals are distributed in equal units.

weighted mean

(denoted Mw) is the combined mean of two or more groups of scores, where the number of scores in each group is disproportionate or unequal

data

(plural) are measurements of observations that are typically numeric.

population parameter

(usually numeric) that describes a population is referred to as a population parameter.

The following g table shows the relative percent distribution for the time in seconds that it took 200 children with attention-deficit disorder (ADD) to show symptoms of the disorder after manipulation. Time (in seconds): Relative percent: 1-6 5% 7-12 5% 13-18 20% 19-24 20% 25-30 30% 31-36 20% Assume that researchers determined that children who showed symptoms of ADD and 18 seconds or less qualified to participate in a new cognitive-behavioral therapy trial thought to help reduce ADD symptoms. How many children qualify for this new treatment? Hint: First convert the data to a cumulative frequency distribution.

60 children qualify for the new cognitive behavioral therapy.

Harwell and Gatti (2001) stated, "If the test score variable possesses an interval scale, then the difference in proficiency reflected in scores of 10 and 15 is exactly the same as the difference in proficiency reflected in scores of 15 to 20" (pg. 105). What is the defining principle that allows researchers to draw this conclusion?

Equidistant scales. Variables on an interval scale have equidistant scales, meaning that differences on this scale are informative.

descriptive statistics

Are producers used to summarize, organize, and make sense of a set of scores or observations. Descriptive statistics are typically presented graphically, in tabular form (in tables), or as summary statistics (single values).

The median is an appropriate measure for describing what types of data?

Data that are skewed and ordinal data.

what is the key distinction between grouped and ungrouped data?

Grouped data are distributed in intervals; ungrouped data are not.

In a second study, Salska and colleagues (2008)distributed a survey to a group of men and women to see what each participant's ideal height would be for a partner. Based on the data given in the table, which gender (men or women) reported ideal height preferences (first row) that most closely approximated the mean height of participants (Second row)? Explain. Women Men Preferences M SD M SD ideal height, 71.3 2.5 65.7 2.6 inches mean participant 65.0 2.5 69.1 2.9 height, inches

Men, because they reported an ideal height that was less than 4 inches shorter than the mean height of female participants. women reported ideal heights that were over 6 inches taller than the mean height of male participants.

Gibson and Myers (2006) investigated perceived wellness among freshman military cadets at the citadel academy. Cadets completed the five factor wellness inventory to measure their perceived wellness pertaining to creative, coping, social, essential, and physical wellness. Total wellness scores ranged from 14.84 to 71.60, with M+ or - SD being 50.00 + or - 9.99. Are these data approximately normally distributed? Explain.

No, the data are likely skewed because the mean is pulled toward the larger scores in the distribution

An animal researcher records the time (in seconds) it takes a group of maze-bright rats to complete a maze. Locate the lower, median, and upper quartiles for the following times. Hint: First arrange the data in numerical order. Time: Frequency: 4 5 5 3 6 1 8 6 12 1 N=16

Q1=4.0, Q2=5.5, Q3=8.0

A sample of 60 scores is distributed with an SS=240. What is the sample variance and sample standard deviation for this distribution?

S2= 240/60-1=4.07; SD= square root 4.07=2.02

A social psychologist records the age (in years) that a sample of eight participants first experienced peer pressure. The recorded ages for the participants were 14, 20, 17, 16, 12, 16, 15, and 16. Compute the SS, the variance, and the standard deviation for this sample using the definitional and computational formula.

SS=37.50, S2=5.36, SD=2.31

The frequency of alcohol-related arrests during a single season at a sporting arena ranged from 0 to 17 arrests per game. What is the interval width if you choose to create a frequency distribution with six intervals?

The interval width for each interval is 3.

The lower boundaries for the number of tattoos among prison inmates are 1,4,7,10,13,and 16. List the value for each upper boundary in this distribution.

The upper class boundaries are 3,6,9,12,15, and 18

A researcher reports the following frequency distribution for the time (in minutes) that college students spent on social networking websites during class time. Identify three errors in this simple frequency distribution. Class Time: Frequency: 0-9 14 9-20 18 21-40 26 40+ 12

Three errors are (1) the intervals overlap, (2) the class width for each interval is not equal, and (3) the distribution includes an open interval.

The upper boundary of one interval and the lower boundary of the next interval do not overlap in a simple frequency distribution. Why?

To ensure that a single score can't be counted in more than one interval

fill in the table below to identify the characteristics of each variable: VARIABLE gender: seasons: time of day: rating scale score: movie ratings (one to four stars): number of students in your class: temperature (degrees fahrenheit): time (in minutes) to prepare dinner: position standing in line: TYPES OF DATA (QUALITATIVE VS. QUANTITATIVE) gender: seasons: time of day: rating scale score: movie ratings (one to four stars): number of students in your class: temperature (degrees fahrenheit): time (in minutes) to prepare dinner: position standing in line: TYPE OF NUMBER (CONTINUOUS VS. DISCRETE) gender: seasons: time of day: rating scale score: movie ratings (one to four stars): number of students in your class: temperature (degrees fahrenheit): time (in minutes) to prepare dinner: position standing in line: SCALE OF MEASUREMENT gender: seasons: time of day: rating scale score: movie ratings (one to four stars): number of students in your class: temperature (degrees fahrenheit): time (in minutes) to prepare dinner: position standing in line:

VARIABLE gender: seasons: time of day: rating scale score: movie ratings (one to four stars): number of students in your class: temperature (degrees fahrenheit): time (in minutes) to prepare dinner: position standing in line: TYPES OF DATA (QUALITATIVE VS. QUANTITATIVE) gender: qualitative seasons: qualitative time of day: quantitative rating scale score: quantitative movie ratings (one to four stars): quantitative number of students in your class: quantitative temperature (degrees fahrenheit): quantitative time (in minutes) to prepare dinner: quantitative position standing in line: quantitative TYPE OF NUMBER (CONTINUOUS VS. DISCRETE) gender: discrete seasons: discrete time of day: continuous rating scale score: discrete movie ratings (one to four stars): discrete number of students in your class: discrete temperature (degrees fahrenheit): continuous time (in minutes) to prepare dinner: continuous position standing in line: discrete SCALE OF MEASUREMENT gender: nominal seasons: nominal time of day: ratio rating scale score: interval movie ratings (one to four stars): ordinal number of students in your class: ratio temperature (degrees fahrenheit): interval time (in minutes) to prepare dinner: ratio position standing in line: ordinal

A researcher reports that increased partying in college (nights per weeks) is associated with a lower grade point average (on the 4.0 grading scale). Does the scatter gram confirm this claim? Explain. See page 65

Yes, as values on the x-axis increase (partying), vales on the y-axis decrease (GPA).

Shook and Fazio (2008) randomly assigned White freshman college students to live with a White (same-race group) or Black (different-race group) roommate in college dormitory. After a few months, researchers measured racial attitudes and compared differences between groups. Is this study an example of an experiment? Explain your answer in terms of randomization, manipulation, and comparison.

Yes, this is an experiment. The race conditions were created by the researchers (manipulation), students were randomly assigned to each condition (randomization), and racial attitudes in two groups were compared (comparison).

fractiles

are measures that divide a set of data into two or more equal parts. fractals include the median, quartiles, deciles, and percentiles, which split data into 2 parts, 4 parts, 10 pars, and 100 parts, respectively

inferential statistics

are procedures used that allow research to infer or generalize observations made with samples to the larger population from which they were selected.

chapter #3 central tendency

are statistical measures for locating a single score that is most representative or descriptive of all scores in a distribution

experiment

a researcher must specifically control the conditions under which observations are made to isolate cause-and-effect relationships between variables. Three requirements must be satisfied for a study to be regarded as an experiment: randomization, manipulation, and comparison.

Pastizzo and Carbone (2007) also looked at Type Count and Token Count by age (from the previous question). The following table shows the frequency distribution of their findings by age. Look at table on page 66. a) Which age group speaks the most? b) Identify two problems with this table that could influence how you interpret the data.

a) 31-50 age group. b) Two problems with this table are that the interval width is not equal, and the table includes an open class (51+).

degrees of freedom (df) for sample variance

are the number of scores in a sample that are free to vary. all scores except one are free to vary in a sample: n-1

interval boundaries

are the upper and lower limits for each interval in a grouped frequency distribution.

a researcher observed a rat respond for food reward by pressing one of three levers in a cage. Pressing the lever to the right (R) produced no food reward, pressing the lever to the left (L) produced a single food pellet, and pressing the lever at the center (C) produced two food pellets. Because the center level produced the largest reward, the researched hypothesized that the rat would press this lever most often. Each trial ended when the rat pressed a lever. The researcher recorded level pressing for 20 trials: L,L,R,L,R,C,R,L,C,L,L,C,C,C,R,C,R,C,L,C,C,L,C,C,C,L,C,C,C,C a) Create an ungrouped frequency distribution for these data b) Do these data support the hypothesis? Explain.

a) Classes: f(x): L 9 C 16 R 5 b) Yes, the rat did press the center lever the most.

An instructor gives students a surprise quiz and records a mean grade of 12 points. What is the new mean value if the instructor: a) Adds 10 points ti each quiz b) Subtracts 2 points from each quiz c) Doubles each quiz score d) Divides each quiz score in half

a) M= 22 b) M= 10 points c) M= 24 points d) M= 6 points

A psychologist measure same of scores on a love quiz, where SD=4 points on this quiz. State the new value for SD if the psychologist a) adds 2 points to each quiz score and b) doubles each quiz score

a) SD=4 b) SD=8

The following table lists the distribution of degrees in psychology conferred by degree-grating institutions, by sex and year. These and similar data are reported by the National Center for Education Statistics (NCES) at http://nces.goc/programs/digest/. Bachelor's degrees: Males: Females: 1970-1971 21,227 14,602 1980-1981 14,332 26,736 1990-1991 16,067 42,588 2000-2001 16,585 57,060 2005-2006 19,865 68,269 a) Based on the data in this table, how has the number roof degrees conferred in psychology changed by sex since 1970-1971? b) Is this a frequency distribution for grouped or ungrouped data? Explain.

a) While more men earned a bachelors degree in psychology in 1970-1971, women earn more than three times the number of bachelors degrees in psychology as of 2005-2006. b) Ungrouped data, because years are not distributed consecutively.

a researcher tests whether cocain use increases impulsive behavior in a sample of cocaine-dependent and cochin-inexperienced mice. a) identify the independent variable in this study b) identify the dependent variable in this study.

a) cocaine use (dependent vs. inexperienced) b) impulsive behavior

The following table lists the number of text messages sent per day in a sample of college students and a sample of their parents. College Students: 43 7 12 50 14 15 13 21 54 21 Parents: 24 21 0 17 20 19 21 5 3 10 a) Compute the mean, the median, and the mode for the college students' and parents' data. b) Based on the shape of the distribution for each sample, which measure of central tendency is most appropriate for describing each sample? Explain how describing each sample with only the most appropriate measure might be misleading.

a) college students: mean=25, median=18, mode=21 parents: mean=14, median=18, mode=21 b) because both distributions are skewed, the median would be the appropriate measure of central tendency. this might be misleading, though, because the median indicates that texting was the same between groups (the median was 18 in both samples), even though differences exist in regard to the mean

If the value of the SS remains constant, state whether each of the following will increase, decrease, or have no effect on the sample variance. a) The sample size increases b) The degrees of freedom decrease c) The size of the population increases

a) decrease b) increase c) no effect

A behavioral scientist measure attention in a sample of 31 participants. To measure the variance of attention, she computes SS=120 for this sample. a) What are the degrees of freedom for variance? b) Compare the variance and standard deviation.

a) df=30 b)S2=120/30=4.0, SD= sure root of 4=2

Wan and colleagues (2008) studied the links between smoking and schizophrenia by gender. In a description of their participants (M+ or - SD), they stated that "of those who reported smoking, men (n=61) and women (n=93) reported...similar daily cigarette consumption per day (men: 4.25 + or - 6.25 cigarettes per day; women: 3.84 + or - 5.26 cigarettes per day)" (pg.428). a) State the degrees of freedom for variance for men and for women b) Assume these data are normally distributed. Is it more likely that men or women smoked at least half pack (10 cigarettes) per day? Explain.

a) df=60 for men; df=92 for women b) men are more likely to smoke at least half pack per day because cigarettes is within 1 SD of the mean for men but greater than 1 SD from the mean for women

What value represents: a) The midpoint of a distribution? Explain. b) The balance point of a distribution? Explain. c) The zero pint of a distribution? Explain.

a) median b) mean c) mean

a quantitative variable varies by _________; a qualitative variable by_________.

amount,class

ungrouped data

are a set of scores or categories distributed individually, where the frequency for each individual score or category is counted.

nominal scales

are measurements where a number is assigned to represent something or someone.

interval scales

are measurements where the values have no true hero and the distance between each value is equidistant.

A family counselor records the number of sessions required for children to complete counseling following the loss of a family member. The counselor finds that most boys completed counseling in 12 sessions, whereas most girls required 15 sessions to complete counseling. If the data for boys and girls are combined, what type of distribution best describes the combined data?

biomodal distribution

operational definition

is a description of some observable event in terms of the specific process by which it was observed or measured.

what are the two types of data that are collected and measured quantitatively?

continuous and discrete numbers

distinguish between data and a raw score

data describes a set of measurements (made up of raw scores); a raw score describes individual measurements

frequency

describes the number of times or how often a category, score, or range of scores occurs.

true zero

describes values where the value 0 truly indicates nothing. Values on an interval scale do NOT have a true zero.

what is the difference between descriptive and inferential statistics?

descriptive statistics summarizes and organizes scores. Inferential draws conclusions and goes beyond the scores from a research study

interval

is a discrete range of values within which he frequency of a subset of scores is contained.

state three commonly used research methods in behavioral science.

experimental, quasi-experimental, and correlational research methods

what is the main distinction between variables on an interval and those on a ratio scale of measurement?

interval variables DO NOT have a true zero, and ratio variables DO have a true zero.

pie chart

is a graphical display in the shape of a circle that is used to summarize the relative percent of discrete and categorical data into sectors.

sample standard deviation

is a measure f variability for the average distance that scores in a sample deviate from their mean. it is calculated by taking the square root of the sample variance

chapter #4 variability

is a measure of the dispersion or spread of scores in a distribution and ranges from 0 to +infinity

datum or raw score

is a single measurement or observation.

relative frequency

is a summary display that distributes the proportion of scores in each interval. it is computer as the frequency in each interval divided by the total number of frequencies recorded.

cumulative frequency

is a summary display that distributes the sum of frequencies across a series of intervals.

pictogram

is a summary display that uses symbols or illustrations to represent a concept, object, place, or event.

normal distribution or symmetrical or gaussian or bell-shaped distribution

is a theoretical distribution with data that are symmetrically distributed around the mean, the median, and the mode

definitional formula for variance

is a way to calculate the population variance and sample variance that requires summing the squared differences of scores from their mean to compute the SS in the numerator

leaf

is located to the right of the vertical line in a stem-and-leaf display. A lead lists the last digit or digits for each number in each row.

range

is the difference between the largest value (L) and the smallest value (S) in a data set.

deviation

is the difference of each score from its mean

upper boundary

is the largest value in each interval of a frequency distribution.

median

is the middle value in a distribution of data listed in numeric order

population size

is the number of individuals that constitute an entire group or population. the population size is represented by a capital N.

sector

is the particular portion of a pie chart that represents the relative percent of a particular class or category.

median quartile

is the portion of data that falls between the 25th and 50th percentile of a distribution of scores

upper quartile

is the portion of data that falls between the 50th and 75th percentile of distribution of scores

lower quartile

is the portion of data that falls in the bottom 25 percent of distribution of scores

interquartile range (IQR)

is the range of distribution of scores falling within the upper and lower quartiles of a distribution

interval width or class width

is the range of values contained in each interval of a grouped frequency distribution.

lower boundary

is the smallest value in each interval of a frequency distribution

science

is the study of phenomena, such as behavior, through strict observation, evaluation, interpretation, and theoretical explanation

mean or arithmetic mean or average

is the sum of a set of scores in a distribution, divided by the total number of scores summed.

sum of squares (SS)

is the sum of the squared deviation of scores from their mean the SS is he numerator in the variance formula

mode

is the value in a data set that occurs most often or most frequently

empirical rule

states that for any normally distributed set of data, at least 97% of data lie within three standard deviates of the mean, at least 95% of data lie within two standard deviations of the mean, and at least 68% of data lie within one standard deviation of the mean.

Miyoshi and colleagues (2008) showed that increased walking among institutionalized patients with dementia was associated with greater weight loss. In their study, they reported that the median distance walked per day for all patients was 1,042.7 meters (m). Because the median was reported, what can we assume about the shape of the distribution of walking among patients in this study?

the data are skewed

state four scales of measurement. which scale of measurement is the most informative?

the four scales of measurement are nominal, ordinal, interval, and ratio. Ratio scale measurements are the most informative

A psychologist records the duration of natural labor (in hours) in a sample of 36 first pregnancy mothers. Based on the duration data given in the following table, which measure of central tendency is most appropriate for describing these data? Hint: draw the shape of this distribution first. 1,5,6,2, 7,3,4,7, 10,7,5,6, 4,3,2,11, 5,9,8,5, 6,6,9,7, 4,5,6,4, 8,8,10,9, 8,7,6,3

the mean because the data are normally distributed, and the duration (n hours) is a ration scale measure.

sample mean

the mean for a sample (or subset of scores from a population)

population mean

the mean for a set of scores in an entire population

A group of researches measure the weight of five participants prior to a clinical wight loss intervention. They record the following weights (in pounds): 200,250,150,100, and 300 pounds. The mean is 2000 pounds. Instead, the researchers reweighed the 300-pound individual and recorded a new weight of 350 pounds. Will the mean increase or decrease in this situation?

the mean will increase

A colleague measures the following heights (in inches) of 10 CEOs selected at random: 72,75,75,66,64,79,79,75,70, and 72. Which measure of central tendency is most appropriate for describing these data? Hint: Draw the shape of this distribution first.

the median because the data are negatively skewed

Patten and colleagues (2008) stated that "among nonsmokers who indicated they were close to a smoker whom they thought should quit, black [participants] were most often concerned about a family member whereas White [participants] endorsed concern most often for a friend" (pg. 496). What are the most common concerns (or mode) for each race?

the mode for nonsmoking black participants was concern about a family member; the mode for nonsmoking white participants was concern for a friend

A group of researches measure the weight of five participants prior to a clinical wight loss intervention. They record the following weights (in pounds): 200,250,150,100, and 300 pounds. The mean is 2000 pounds. The researchers implemented their weight loss intervention with the original five participants and found that each participant lost exactly 10 pounds in the first 3 weeks. Without recalculating the mean, what is the new mean weight?

the new mean weight is 190 pounds

A researcher selects a sample with a sample variance of 36. If she computed the sample variance by dividing SS by (n-1), then what other value will also be qual to 36 on average?

the population variance

State four characteristics of the standard deviation.

the standard deviation is always positive, is used to describe quantitative variables, typically reported with the mean, and it affected by the value of every score in a distribution

What does the standard deviation measure?

the standard deviation measure the average distance that scores deviate from their mean

A sample of 26 patients with major depressive disorder (MDD) showed an average of five symptoms of the disorder prior to diagnosis. What is the sun of the differences of scores from the mean in this sample?

the sum of the differences of scores from the mean is 0

What does it mean to say that the sample variance is unbiased?

the variance of the sample will equal the variance of the population from which the sample was selected on average

cumulative relative frequency

us a summary display that distributes the sum of relative frequencies across a series of intervals.

quantitative variable

varies by amount. this variable is measure numerically and is often collected by measuring or counting.

qualitative variable

varies by class. This is often represented as a label and describes nonnumeric aspects of phenomena.

A cognitive psychologist is interested in the ability of men and women to multitask--a cognitive skill thought to engage short-term or working memory. The psychologist observed a sample of 5 men (n=5) and 8 women (n=8) and measured the number of tasks they could accurately complete within a short time frame. He found that men completed 2.3 tasks on average (M=2.3), whereas women completed 4.5 tasks on average (M=4.5). What is the weighted mean for both samples? Hint: The overall mean is not 3.4 tasks.

weighted mean = 3.65