Metod 2: 2 Flashcards
(30 cards)
Explain the concepts of Type I and Type II errors.
Type I error: False positive (rejecting a true null hypothesis).
Type II error: False negative (failing to reject a false null hypothesis).
What does “statistical significance” mean?
The observed result is unlikely due to chance alone (typically p < .05).
What is a p-value?
The probability of observing the data, or more extreme, assuming the null hypothesis is true.
What is a confidence interval?
A range of values within which the true population parameter likely falls.
What does the width of a confidence interval indicate?
Narrow = more precise estimate; Wide = less precise estimate.
What assumptions apply to a t-test?
Normal distribution, independence of observations, and homogeneity of variance (for independent t-test).
What does “normal distribution” mean?
A symmetric, bell-shaped distribution where most values cluster around the mean.
How do you assess normality in SPSS?
Using histograms, Q-Q plots, Shapiro-Wilk test, and skewness/kurtosis values.
What is the difference between descriptive and inferential statistics?
Descriptive: Summarizes data. Inferential: Draws conclusions about populations based on samples.
What is the purpose of a boxplot?
To visualize the distribution, spread, and potential outliers in data.
How does sample size affect a confidence interval?
Larger sample = narrower confidence interval.
Why is it important to report effect size?
To show the magnitude of a result, not just whether it is statistically significant.
What is the difference between independent and dependent samples?
Independent: Different participants in each group. Dependent: Same participants measured multiple times.
Describe what the interquartile range (IQR) represents.
The range between the 25th and 75th percentiles (middle 50% of the data).
In a boxplot, what do the whiskers represent?
The range within 1.5 * IQR above and below the quartiles.
What are outliers and how are they visualized in a boxplot?
Extreme values outside 1.5 * IQR; shown as circles or stars.
Explain the concepts of mean, median, and mode.
Mean: Average. Median: Middle value. Mode: Most frequent value.
What is the standard deviation?
A measure of how spread out numbers are around the mean.
What is standard error?
An estimate of how much the sample mean deviates from the population mean.
How is the t-value calculated in an independent samples t-test?
Difference between group means divided by pooled standard error.
What does “variance” mean?
The average squared deviation from the mean.
What is the relationship between standard deviation and variance?
Standard deviation is the square root of variance.
When should you use a paired samples t-test instead of an independent samples t-test?
When comparing two related measurements (e.g., before and after treatment on the same subjects).
In SPSS, what does the Explore function generate?
Descriptive statistics, plots (boxplots, histograms), and normality tests.
