Population vs Sample
A school has 800 students. You survey 100 of them. Is this a population or a sample?
Sample
What is the main purpose of using a random sample?
To avoid bias and fairly represent the population
What do we call a prediction about a population based on data from a sample?
Population Inference
Find the mean: 5, 10, 15, 20.
12.5
In a dot plot, what does stacking multiple dots above a value mean?
That value occurs multiple times
DOUBLE YOUR TEAMS SCORE
GOOD JOB!!
Which sampling method is random:
A) Picking every third person
B) Drawing names from a hat
B) Drawing Names from a hat
True or False — If a sample is biased, the inference might be inaccurate.
True
Find the median: 10,4,11,3,9
9
What are the five numbers in a box plot’s five-number summary?
Minimum, Q1, Median, Q3, Maximum
Which is more accurate: surveying a whole population or a sample?
Whole Population
A teacher surveys the first 5 students in the hallway. Is this random?
No
If 30 out of 50 sampled students like basketball, predict how many out of 200 students would like it.
120
How is IQR found?
Q3-Q1
True or False — A box plot shows both mean and median.
False (only median)
Out of these, which is a population?
A) All 7th graders in the country
B) 50 randomly selected 7th graders
A) All 7th graders in the country
If a survey is done by choosing numbers on a number generator, what type of sampling is it?
Random
The larger the random sample, the more likely the inference is __________.
Accurate (Or reliable)
LOSE ALL YOUR TEAMS POINTS
If a box plot’s box is very wide, what does it tell you?
There’s a large spread in the middle 50% of the data
True or False — A good sample should be as large as possible to perfectly represent the population.
False (as large as needed, but must be random and unbiased — perfection is impossible)
Swap points with the team to your right on the screen!
Interesting...
If a sample of 20 students out of 500 is randomly selected, is it safe to infer for the whole group?
No (too small to be reliable — larger sample is better)
Find the IQR: 1, 3, 5, 7, 9, 11, 13.
8
A box plot has a median of 50, Q1 of 45, and Q3 of 55. What is the IQR?
10