(Midterm) Z score Flashcards
What is the primary purpose of a z-score?
To describe the exact location of a score within a distribution.
The numerical value of the z-score corresponds to the _____________________
number of standard deviations between X and the mean of the distribution.
Z-scores identify ____________ within a distribution means.
exact locations
Z-scores can be used as ____________________ & ________________________
descriptive statistics and as inferential statistics.
As ___________, z-scores determine whether a specific sample is representative of its population, or is extreme and unrepresentative.
inferential statistics
What is the advantage of standardizing distributions?
Two (or more) different distributions can be made the same.
Probability is the ______________________.
We define probability as a fraction or a proportion.
Method for measuring and quantifying the likelihood of obtaining a specific sample from a specific population
The probability of any specific outcome is determined by a ________________
Ratio comparing the frequency of occurrence for that outcome relative to the total number of possible outcomes. (Fo/Po)
When a population of scores is represented by a frequency distribution, probabilities can be defined by_____________
proportions of the distribution.
In graphs, probability can be defined as a _______________
proportion of area under the curve.
Why is probability important?
Probability is important because it establishes a link between samples and populations.
What is the general goal of inferential statistics?
To use the information from a sample to reach a general conclusion (inference) about an unknown population.
Two requirements of a random sample
- Each individual in the population has an equal chance of being selected
- If more than one individual is to be selected for the sample, there must be constant probability for each selection
What is the definitions of “distribution of sample means”?
the set of X‘s for all the possible random samples a specific sample size (n) that can be obtained from a given population
The parameters of the distribution of sample means (acc to central limit theorem):
1.
2.
3.
- shape (normal, n=30 or more)
- central tendency
- variability
What do you call the mean of the distribution of sample mean?
Expected value of X
The standard deviation of the distribution of sample means is called the _______
standard error of X
What does the standard error do?
Measures the standard distance between a sample mean and population mean
The________tells how much error to expect if you are using a sample mean to estimate a population mean
standard error
State the law of large numbers
The larger the sample size (n), the more probable it is that the sample mean will be close to the population mean
______________ involves using sample statistics to make a general conclusion about a population parameter. The standard error plays a crucial role in inferential statistics
Statistical inference
____________________ is an inferential procedure that uses the data from a sample to draw a general conclusions about population.
Hypothesis testing
4 steps of hypothesis testin
- State the null hypothesis
- Locate the critical region
- Collect the data, and compute the test statistics
- Make a decision
Two types of errors that can be committed
Type I error
Type II error
Occurs when a researcher rejects a null hypothesis that is actually true
type I error
Occurs when a researcher fails to reject a null hypothesis that is really false
type II error
When do we use one tailed tests?
> When a researcher predicts that a treatment effect will be in a particular decision (increase or decrease)
When there is a prior justification for making a directional prediction.
What is the probability that the test will correctly reject the null hypothesis.
Power of the hypothesis test
As the size of the treatment effect increases, statistical power ______
increases
FACTORS THAT CAN INFLUENCE POWER
A. increasing alpha level
B. A one tailed test will have greater power than a two tailed test
C. A large sample will result in more power than a small sample
