Stats Exam 1

A researcher is interested in the relationship between IQ and self esteem. She collects IQ and self esteem scores from tests administered to subjects to examine the relationship. This is an example of

a correlational study

Number of goals scored by a soccer player during a game is an example of

a discrete variable

skewed distribution

a distribution that has a small number of extreme scores

unimodal distribution

a distribution with one mode

A survey asks participants to state their ethnicity. This is an example of

a nominal scale

A researcher is interested in whether or not snakes can detect insults. He buys 20 exotic snakes, and separates them into two groups of 10. For one group of snakes, he insults them for 10 minutes each. For the other group, he simply stares at them for 10 minutes each. For each group, he records the number of times the snakes bite him (assuming that a bite indicates that the snake took offense to him). At the end of the experiment, the group of snakes he insulted had bit him 23 times vs. only 8 bites from the group he did not insult. a) What type of study? b) What is the independent variable? c) What is the dependent variable? d) Is the dependent variable discrete or continuous? e) What is the scale of measurement for the dependent variable? f) Name one confounding variable?

a) experimental study b) insult level (insult/no insult) c) number of snake bites d) discrete (bar graph & counting) e) ratio (relation between two amounts) f) snake breed, noise (influences the iv & dv)

ratio scale

an interval scale with an absolute zero point (reaction time, height, errors on test, Kelvin temp)

Suppose 50 people take a math exam-25 math experts and 25 people very poor at math. This distribution will probably be

bimodal

bimodal distribution

distributions with two modes

A score has a deviation score of zero. The value of the score must be:

equal to the mean of the distribution

continuous variable

histograms, used for measuring

In an experiment, the variable that is purposely manipulated is the

independent variable

continuous variable

infinite number of possible values (time, weight, etc)

For a symmetric distribution, the mean

is equal to the mode and median

Which distribution would have lower variability, a leptokurtic distribution, or a platykurtic distribution?

leptokurtic (less consistent)

For a negatively skewed distribution, the mean is:

less than the median

The _____ divides a frequency distribution exactly in half

median

quasi-experimental study

no actual manipulation, groups defined by "natural variations", either between subjects or over time (ex: study looking at gender differences, cant assign genders)

We conduct a survey asking spectators at a car race what brand of car they own (e.g."Chevrolet", "Honda", "VW" etc). What is the scale of measurement for our variable, the brand of car. If we wanted to make a diagram of the results, what type of graph should we use in this case?

nominal scale (categories with names), bar graph

interval scale

ordered categories that are all intervals of exactly the same size (temp in Fahrenheit, IQ scores)

The direct, unchanged scores that are the direct result of measurement are called:

raw scores

discrete variables

separate, indivisible categories: bar graphs, used for counting (number of goals scored)

variance

standard deviation squared

case study

study of one individual in great detail

mean

the average

mode

the most frequently occurring score(s) in a distribution

experimental study

the researcher manipulates one of the variables and tries to determine how the manipulation influences other variables

standard deviation

the square root of the variance

In a normal distribution, the relationship between the mean and median is such that

they are equal

correlational study

two (or more) variables are observed to determine if there is a relationship (nothing being manipulated)

For a positively skewed distribution, the mean

usually has a larger value than either the median or the mode

ordinal scale

values are categories assigned in an ordered sequence or rank (places in a race, olympic medals)

nominal scale

values are categories that differ only in name (gender, ethnicity, eye color, numbers on cars)

For any distribution, regardless of its shape, the sum of the deviation scores will always be

zero