1. Ungraded quiz
Unit 7

2. Show me your fingers
Do not shout out the answer, or your classmates will follow what you said.
Use your fingers
One finger (the right finger) = A
Two fingers = B
Three fingers = C
Four fingers = D
No finger = I don’t know. I didn’t study

3. What is the difference between discriminant analysis (DA) and cluster analysis (CA)?
In DA the analyst needs to assign the number of clusters in advance while CA is entirely exploratory..
DA aims to assign observations into existing groups while CA is intended to discover new grouping patterns.
DA starts with a centroid but CA can start anywhere.
All of the above.

4. Which of the following statements is true?
In normal mixtures the data must be categorical.
In latent class analysis the data must be continuous.
In K-mean clustering the data can be continuous and categorical.
Two-step clustering accepts both continuous and categorical data.

5. Which of the following about DBSCAN is true?
DBSCAN is available in SAS.
K-mean clustering might fail to detect a string-like clustering pattern but DBSCAN can detect any shape of clustering.
DBSCAN separates concentrated data from sparse data.
All of the above.

6. Which of the following about hierarchical clustering (HC) is true?
HC can be top-down or bottom-up.
HC and MDS can work hand in hand if the row items and the column items are the same in a symmetrical data matrix (e.g. R1 = C1, R2 = C2…etc.).
Besides grouping observations into a few clusters for data reduction, HC can also be used for matching two individuals into a pair.
All of the above

7. Which of the following about two-step clustering is true?
In two-step clustering a pre-cluster is created in step 1.
In two-step clustering if the model quality index is less than 0.5, then it is considered a poor model.
Two-step clustering tends to create asymmetrical clusters.
All of the above.

8. Which of the following about EFA and PCA is true?
When the user requests factor analysis in SPSS, the default is PCA.
PCA is a data reduction method that does not require any causal structure or theoretical justification.
EFA can be used to confirm the factor structure.
All of the above.

9. Which of the following statement about vector is true?
A vector consists of scalars.
A vector contains both the numeric and directional information.
Vectors are used in the subject space.
Eigenvectors visually depict eigenvalues.
All of the above.

10. What of the following is true?
A loading plot shows the relationship and the grouping patterns of variables, which are represented by vectors.
The cosine of the angle between two vectors is the same as Pearson’s r.
The biplot shows both the observations and the vectors.
All of the above.

11. Which of the following statement about parallel analysis (PA) is true?
PA is based on resampling (bootstrapping).
PA with PCA tends to over-factoring.
PA with EFA tends to under-factoring.
PA can be run in SPSS only.