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