PSYC 210 _ Ch 3
negatively skewed distribution
A distribution in which most scores are substantially smaller (left side of the graph) than most others.
bimodal distribution
a distribution of scores in which two scores occur most often or most frequently. 2 MODES
positively skewed distribution
a distribution of scores that includes one or a few scores that are substantially larger (toward the right tail in a graph) than most other scores.
skewed distribution
a distribution of scores that includes outliers or scores that fall substantially above or below most other scores in a data set
normal distribution
a distribution where the scores are similarly distributed above and below the mean, median, and mode at the center of the distribution.
summing the squared differences of each score from its mean produces what? And if you replace the mean with any other value what happens?
a minimal solution; the solution will be larger.
the median is the preferred descriptive statistic: a) skewed distributions and ordinal data b) ordinal data c) skewed distributions and ratio scale data d) normally distributed and interval and ratio scale data
a) skewed distributions and ordinal data
State the characteristic of the mean that indicates that the mean is the zero point for a distribution of scores.
the sum of the differences of scores from their mean is zero.
a distribution of scores in which only ONE score occurs most often or most frequently. ONE mODE
unimodal
What is measure of central tendency?
values at or near the centre of a distribution
When is weighted mean used?
when sample sizes are not equal
what happens when the median has a value to the tenths place (.5)?
you have to average the 2 scores surrounding the median
the difference of each score from the mean always equals what?
0 (imagine balancing weights on both sides of a scale)
what type of distribution can be used to estimate the value of the median?
50th percentile of a cumulative percent distribution
the mean is the preferred descriptive statistic: a) for describing normal distributions b) for summarizing interval scale measures c) for summarizing ratio scale measures d) all of the above
D) All of the above
which type of modal distribution would not be described using the mode? A) UNIMODAL B) BIMODAL C) MULTIMODAL D) NONMODAL
D: NONMODAL
what is the population mean symbol?
Mu
do outliers influence the mean and median?
No, only influence the mean
The median is a) the preferred measure of central tendency when outliers are in a data set b) the middle value in a distribution listed in numerical order c) at the 50th percentile of a cumulative percent distribution d) all these
d
the mode is typically used to describe: a) interval score b) modal distributions c) nominal scale data d) nominal scale data and modal distributions
d
add a score below the mean and the mean will [blank]?
decrease
delete a score above the mean and the mean will [blank]?
decrease
true or false: the mean is a preferred measure for describing skewed distributions.
false: the median is the preferred measure
true or false: the mean is greater than the mode, the distribution is negatively skewed.
false: when the mean is less than the mode, the distribution is negatively skewed.
what is another term for a normal distribution?
gaussian
add a score above the mean and the mean will [blank]?
increase
delete a score below the mean and the mean will [blank]?
increase
As a rule, when you [increase] the value of an existing score, the mean will [blank]; when you [blank] the value of an existing score, the mean will decrease.
increase; decrease
What are the measures of central tendency?
mean, median, mode
the [blank] is the preferred measure of central tendency when a data set has outliers
median
A distribution of scores in which one or more scores occur most often or most frequently
modal distribution
a distribution of scores where more than two scores occur most often or most frequently. Has more than two modes
multimodal distribution
The mode is the primary measure of central tendency to describe data on which scale of measurment?
nominal
what is a distribution that has no mode?
nonmodal distribution
Add or delete a score equal to the mean and the mean will [blank}?
not change
why is the mean appropriate for describing ordinal data?
ordinal data convey direction only (more or less than)
what does 'N' stand for?
population size
What does "n" stand for?
sample size
what usually happens when you change each score in a distribution by the same constant?
the mean will likely change by the same constant
what is the median
the midpoint in a distribution (middle score)
what does sigma mean?
the sum of