Pre Exams 1
What value represents: a. The midpoint of a distribution? Explain.
Median
Sample Size
# of individuals that constitute a subset of those selected from a larger population (n)
Population Size
# of individuals that constitute an entire group or population (N)
Based on the empirical rule what percentage of data fall within 1 SD, 2 SD, and 3 SD of the mean for data that are distributed normally?
1 SD: 68% 2 SD: 95% 3 SD: 99.7%
List five characteristics of the mean.
1. Changing the existing score will change the mean 2. adding a new score completely removing an existing score will change the mean, unless the value equals the mean 3. Adding, subtracting, multiplying or dividing each score in a distribution by a constant will cause the mean to change by the constant 4. the sun of differences of scores from their mean is zero 5. the sum of the squared differences of scores from their mean is minimal
How to find the Lower Median, Median and Upper Median
1. Find the mean for all data 2. locate the median for the Q1 scores below the Q2 3. locate the median for the Q3 scores above the Q2
Type of Number
Continuous or Discrete
Distinguish between data and a raw score.
Data are measurements or observations that are typically numeric and they are made up of raw scores. A raw score is a singular measurement or observation.
The median is an appropriate measure for describing what types of data?
Data that are skewed or ordinal
What value represents: The balance point of a distribution? Explain.
Mean
What value represents: The zero point of a distribution? Explain.
Mean
What is central tendency?
Measures of central tendency are statistical measures used to locate a single score that is most represented or descriptive of all scores in a distribution.
Can variability be negative? Explain
No because variability is a measure of distance and you can't have a negative distance
Researchers are interested in studying whether personality is related to the month in which someone was born. a. What scale of measurement is the month of birth?
Nominal
4 Scales of Measurement
Nominal, Ordinal, Ratio, Interval
Scale of Measurement
Nominal, Ordinal, Ratio, Interval
How do the sample mean and the population mean differ?
Population mean is the mean for a set of scores of an entire population where as sample mean is the mean for a sample or subset of scores from a population
Type of Data
Qualitative or Quantitative
Gender
Qualitative, Discrete, Nominal
Seasons
Qualitative, Discrete, Nominal
Time of Day
Quantitative, Continuous, Ratio
Temperature
Quantitative, continuous, interval
Time (in minutes) to prep dinner
Quantitative, continuous, ratio
Rating Scale Score
Quantitative, discrete, interval
Movie Ratings (one to four)
Quantitative, discrete, ordinal
Position standing in line
Quantitative, discrete, ordinal
Number of students in class
Quantitative, discrete, ratio
Explain why deviations from the mean are squared in the formula for variance.
Squaring allows us to get rid of the negative in order to know how far the distance is from the mean (looking at it from the perspective of standard deviations)
What is the interquartile range?
The IQR is the range of the distribution of scores falling within the upper and lower quartiles of a distribution (IQR=Q3-Q1)
What is the main distinction between variables on an interval and those on a ratio scale of measurement?
Variables on an interval scale do NOT have a true zero and have equidistant scales and variables on a ratio scale are also equidistant but HAVE a true zero.
Can a nominal variable be numeric? Explain.
Yes because you can code a categorical variable numerically. Ex. January could be 1 and February could be 2...etc.
Researchers are interested in studying whether personality is related to the month in which someone was born. b. Is it appropriate to code the data? Explain.
Yes each month could be represented by a number
The mean is an appropriate measure for describing what types of data?
can be used with both discrete and continuous data used mostly with continuous (on interval and ratio scale) that are normally distributed
State whether it is continuous or discrete data. a. Time in seconds to memorize a list of words
continuous
State whether it is continuous or discrete data. c. The weight in pounds of newborn infants
continuous
State whether it is continuous or discrete data. b. Number of students in a statistics class
discrete
State whether it is continuous or discrete data. d. The SAT score among college students
discrete
Examples of Ordinal
indicate order alone; rankings, grade level
Compute the median
n PLUS 1 divided by 2 which finds the number spot and then you go to that spot in the order and find that number
Compute the mode
number that occurs most often
Examples of Interval
rating scale, temperature
Population Mean
sum of N scores divided by N (mu) mu=sum of N scores (sum of x) /N
Sample Mean
sum of n scores divided by n (M) M=sum of n scores (sum of x) /n
Compute the sample mean
sum of x divided by the n (sample size)
What does the standard deviation measure?
the standard deviation measures the average distance that scores deviate from their mean
Examples of Ratio
time of day, number of students in a class, time to prepare dinner, weight, height, calories
Examples of Nominal
typically coded; seasons, months, gender
The mode is an appropriate measure for describing what types of data?
used to describe modal distributions of data and measurements on a nominal scale
Continuous
variable is measured along a continuum at any place beyond the decimal point
Discrete
variable is measured in whole units or categories that are not along a continuum