Stats 2242 Midterm Flashcards
What are the values representing a population?
parameters
What’s the difference between finite population and infinite population?
Finite has a limited number of units (ex: students in class)
Infinite has no limit to units that could potentially belong to it.
(ex: students enrolled in all universities)
What is a sample? what are the values that represent it called?
A sample is a subset of units making up a group of interest. Statistics are the values that make up a sample.
What are variables? Give some examples.
Variables are any trait that differs within a population. Height, weight, age, salary
What is the difference between discrete quant variables and continuous quant variables?
Discrete can be counted by whole numbers. Continuous is obtained by measuring. The # measured is often beyond the decimal point (ex: wait time)
What are collectively exhaustive qualitative variables?
Collectively exhaustive variables cover all possible outcomes. Can include “other” option
What is the difference between nominal scales and ordinal scales?
Nominal scales (name a category) classify info into categories with no order in the categories (ex: gender or colors). Ordinal scales (order) classify info into categories with logical underlying defining the categories. (ex: satisfaction levels low-high), education levels)
What is the difference between descriptive and inferential stats?
Descriptive stats don’t test hypothesis but just describe a set of data meaningfully. Inferential stats test hypothesis.
What is the difference between probability and non- probability sampling?
In probability units are selected randomly. It’s unbiased (everyone = % of being picked). Non-probability sampling is selecting people based on non-scientific criteria. It’s biased (not an = % of being picked) and non-representative.
what is Sampling?
Sampling is taking a subset of units from a larger population.
What’s the difference between sampling with/without replacement?
With replacement a unit can be picked more than once. Without replacement a unit can only be picked once.
What are the 3 steps to random sampling?
- Create a numbered list of all units in a population.
- Generate a list of random numbers.
- Match random numbers to participants in sampling frame to obtain final sample.
What is systematic random sampling?
Create sampling frame
2. N/n for k
3. start at a random spot
4. Sample every Kth value from the starting spot until n is reached.
What is Stratified Random sampling?
- Divide population into groups
- Select random sample from each group preserving group proportions
- Combine samples to yield total at the end.
(Ex: surveying 15 students from each residence)
what is Cluster sampling?
- Divide population into sub populations
- Randomly select one or more clusters.
- add together to yield total
(ex: surveying Elgin and Med Syd)
What is Multi-Stage Sampling?
This combines the first two methods.
1. Divide population
2. Pick out clusters
3. Survey a sample of each cluster
What is convenience sampling?
Sampling people that are most convenient or available.
What is voluntary sampling?
It’s sampling members of a population that respond to recruitment.
What are strata?
They are groups found in random sampling.
provide an example of inferential and descriptive stats.
Inferential: two groups of students study different. Which group had better test scores
Description: these are the classes test scores.
