Quantitative Data Analysis Flashcards
What is a null hypothesis?
- The null hypothesis is the base line
- In experimental research the null hypothesis is that nothing will change
- We accept or reject the null hypothesis
What is an experimental hypothesis?
- The experimental hypothesis is what we predict
- We can have more than 1 experimental hypothesis
What is a Type I Error?
When we reject a null hypothesis that is true.
What is a Type II Error?
When we do not reject a false null hypothesis (we accept a null hypothesis that is false).
What are the 4 stages in the process of hypothesis testing?
- Hypothesis formulation
- Specification of significance level
- Selection of appropriate statistical test
- Calculation of the test statistic and acceptance or rejection of the hypothesis
Types of hypothesis
- hypothesis about a single population
- hypothesis about comparisons between two groups
- hypothesis about the relationship between variables
What is the significance level?
- The significance level measures the probability of making a mistake
- The significance level has to be decided on the basis of the expected consequences of a type I error and a type II error, before the test is conducted
What is the significance level if we believe a type I error is more severe?
0.01 or 0.001
What is the significance level if we believe a type II error is more severe?
0.1
What is the significance level if we believe a type I error and a type II error are equally severe?
0.05
Selection of appropriate statistical test
The selection of the test depends on the type of data we have collected
What are the types of data?
Categorical and Quantifiable
What are the types of categorical data?
Nominal and Ordinal
What are the types of quantifiable data?
Interval and Ratio
What is Nominal data?
Nominal data constitute a name value or category with no order or ranking implied
What is Ordinal data?
Ordinal data comprises an ordering or ranking of values, although the intervals between the ranks are not intended to be equal
When do we use Ordinal data?
Ordinal scales are used for questions that rate the quality of something and agreements
What is Interval data?
Numerical values are assigned along an interval scale with equal intervals, but there is no zero point where the trait being measured does not exist.
What is Ratio data?
Ratio data are a subset of interval data, and the scale is again interval, but there is an absolute zero that represents some meaning.
When do we use a One-sample t-test?
When we have one variable of interest and that variable is quantifiable.
What test do we use when the independent variable is nominal and the dependent variable is quantifiable?
Dependent t-test or Independent t-test
When do we use Regression analysis?
When we have two variables of interest and they are both quantifiable.
What is the One-sample t-test
A statistical test based on the mean and the standard deviation of the data when the variable of interest is quantifiable
How do we determine if we reject H0?
To determine if we should reject H0 or not, we compare the probability of making a type 1 error in this test (the p-value or Sig. in SPSS) with the significance level we set.
If p-value < sig.level: reject H0.
If p-value > sig.level: do not reject H0.
How do we write a conclusion?
We always refer to the t statistic and the p value.
Example:
Conclusion:
We reject H0. There is enough evidence to infer that the new machine packs faster than the old machine (t = -6.416, p-value = 0.000).
What are the Dependent t-Test and Independent t-Test?
Both tests compare the average value of a dependent variable between two groups (independent variable).
When do we use the Independent t-Test?
When we compare the average value of the dependent variable between two independent groups.
Example: People who have received the IELTS training vs people who have not
When do we use the Dependent t-Test?
When we compare the average value of the dependent variable for one group, twice.
Example: English proficiency before and after the IELTS training
What is the advantage of the Dependent t-test over the Independent t-test?
The advantage of the dependent t-test is that it controls for extraneous variables.
What is Regression analysis?
In regression analysis we test if there is a linear relationship between the independent and dependent variable and if this relationship is positive or negative.
- We want to come up with a model to predict the relationship
