Sampling Methods
Using a number generator to select 10 random people that live in Middlesex County
SRS
x bar
sample mean
What is the probability of flipping 2 coins and getting heads on both of them?
(.5)(.5) = .25
The mean weight of dogs is 41 pounds, interpret this
When weighing lots and lots of dogs, the average weight is 41 pounds
Why and How do you check for large enough sample for a means problem?
To determine if dist is approx normal
Use CLT n>30
Grouping students by grade level, then selecting 2 from each grade level
stratified
Mu
Population mean
When starting a difficult mower, what is the probability that it takes 4 pulls before it starts, given that the probability of it starting is .47, and that each pull is independent
Geometric (pdf)
p=.47, x = 5
.037
The standard deviation of dogs' weights is 15 pounds, interpret this
On average dogs' weights vary from the mean by 15 pounds
Why and How do you check large enough counts for a proportions problem?
To see if distr is approx normal
np > 10 and n(1-p) > 10
Looking at all the schools in Virginia, then randomly selecting 5 schools and talking to every student in those schools
Cluster sample
P hat
sample proportion
P(A) = .45
P(B) = .16
A and B are mutually exclusive. Determine P(A and B)
Interpret resistance using the situation
In a graph that is skewed right we know that the mean....the median...
The mean will be higher than the median since the median is more resistant to the high values
What is the check for the standard deviation calculation?
Independence - sample size is less than 10% of the population
Taking a roster of all MHS students then selecting every 12th student to talk to
Stratified
Mu p hat
The mean of the sampling distribution of proportions
P(A) = .4
P(B) = .35
A and B are independent. What is P(A|B)
P(A|B) = .4
Since they are independent B happening does not affect A
When asked to interpret or describe a graph what is expected?
CUSS - Center, unusual, shape, spread in context
When calculating a probability and the calculator gives you an answer of 4.879 what should you check for?
Since probability is between 0-1, check for scientific notation - or an error