Stats Flashcards
Sub-collection of members selected from a population
Sample
Influenced by another factor, it’s the one you’re measuring
Dependent variable
Influences the dependent factor and is controlled by the researcher
Independent variable
Mathematical description of a population characterisitic
Parameter
Mathematical description of a sample characteristic
Statistic
Used to summarize and describe the characteristics of data numerically and graphically
Descriptive statistics
Make conclusions about populations
Inferential statistics
Consists of names or labels
Categorical data
Consists of numbers representing counts or measurements
Quantitative data
Finite number or countable
Discrete
Infinitely many possible values
Continuous
Names, labels, or categories only and the data cannot be arranged
Nominal level measurment
Arranged in some order but differences can’t be determined or are meaningless
Ordinal level measurement
Ordinal level with the additional property that there is a difference between two values however there is NO natural zero
Interval level measurement
Interval level with a natural zero starting point. The differences of the values are meaningful
Ratio level measurement
Categories onlly
Categories w/ order
Differences but no natural start
Differences and a natural start
Nominal
Ordinal
Interval
Ratios
Apply some treatment and then observe its effects on the subjects
Experimental study
Observing and measuring specific characteristics w/o attempting to modify the subjects
Observational study
N subjects are selected in a way that every possible sample size N has the same chance of being chosen
Simple random sample
Select some starting point and then select every kth element
Systematic sampling
Subdivide the population into subgroups that share characteristics and then draw a sample from each
Stratified sampling
Divide the population into section and randomly select some of those clusters and chose ALL members from those clusters
Cluster Sampling
Collect data by using some combination of the basic sampling methods, pollsters select sample in different stages
Multistage sampling
Chooses itself by responding to a general appeal
Voluntary response sample
Results that are easy to get
Convenience sample
Equation for relative frequency
= class frequency/sum of all
On a histogram, what do the horizontal and vertical scales represent?
Horizontal - classes
Vertical - frequencies
Scatter plots are a graph of x,y plots used for what?
Determine relationship b/w x and y
When two values are somehow associated with each other
Correlation
Measures the strength of the linear relationship b/w x and y
Linear correlation coefficient, r
What value of the Pearson correlation coefficient, r, is considered very strong and strong
Very - .8 to 1.0
Strong - .6 to .8
What is the only measure of center that can be used with nominal data
Mode
What 3 measures of variability are commonly used?
Range
SD
Variance
A measure of the variation of values about the mean, represents the average amount of variability in a set of scores
Standard Deviation
A measure of variation equal to the square of the standard deviation
Variance
The number of standard deviations that a given value x is above or below the mean
Z score
Z score equation
z = (value - mean) / SD
The mean and SD of the z-scores of a population are always?
Mean = o
SD = 1
Z score values…
Ordinary and Unusual values
Ordinary - Z score between 2 and -2
Unusual - Z score greater than +2 or less than -2
P(A) means…?
Probability (% chance) that A happens/is chosen
Explain the probability addition rule
Probability event A OR event B occurs
add the fractions
Explain the multiplication rule for probability
Probability that event A AND B occur
A and B are independent
multiply the fractions
A series of independent trials where each trial has two possible outcomes/events
A procedure
Area under a density curve is a correspondence between…?
Area and probability
Approximates a normal distribution as the sample size increases regardless of the distribution of the population
Sample mean
Gives us a range of values with certain probability to contain the population mean
Confidence interval
What happens to the confidence interval as the sample size increases
The confidence interval DECREASES
The definitive statement that there is a relationship b/w populations regarding certain variable
Research Hypothesis
What is a non-directional research hypothesis?
A difference between groups but doesn’t specify the direction
What is a Directional research hypothesis
There is a difference between groups AND specifies direction
States that there is no difference b/w conditions or a condition and a specified value
Null hypothesis - it is the starting point against which actual outcomes can be measured
A standard procedure for testing a claim about a property of one or more populations
Hypothesis test
OR
Test of Significance
A value used in making a decision about the null hypothesis.
Test Statistic
How to find the Test Statistic
Converting the sample statistic to a score with the assumption that the null hypothesis is true
Reflects the uncertainty in the mean estimated from a sample
Standard Error of Mean
Probability of getting a value of the test statistic that is at least as extreme as the one representing the sample data assuming that the null hypothesis is true
P value
What is the significance of a P-value:
- Less than or equal to alpha
- Greater than alpha
Less than or equal to A = rejects the null
Greater than A = fail to reject the null
The mistake of rejecting the null when it is actually true
Type I error
The mistake of failing to reject the null when it is actually false
Type II error
