Post on 18-Jan-2018
description
Recap…
We need to take spread into account when we give an interval for the population parameter
So far…
Population
Sample
Sample statistics
Population
parameterWhat we’re trying
to estimate
So far…
Population
Sample
Sample statistics
What is the median
weights of kiwis?
What we’re trying to estimate
Take your sample of kiwis•Dot plot•Box plot•Sample statistics…
So far…
Population
Sample
Sample statistics
Population
parameterWhat we’re trying
to estimate
Median weight of kiwis is somewhere between ___ and ___
Samples of size ___ were reliable enough
The median weight of kiwis was somewhere between ___ and ___(90% ish of our sample medians)
Distribution of sample medians…
2.2 2.4 2.6 2.8 3.0 3.2median
Measures from Sample of Kiw ipop Dot Plot
We don’t get to take multiple samples so this process WON’T work We need to find an informal confidence interval for the population median based ON A SINGLE SAMPLE
However in real life …
To take into account both•Sample size and•spread
Our informal interval needs…
For your sample of kiwis:•Dot plot•Box plot•Median
More kiwis…
Add your SAMPLE MEDIANS TO THE SHEET
Then
Add your IQR (box) TO THE SHEET
Student worksheet
Complete Q3 – Q5 on the worksheet
Student worksheet
Q3: I notice that the width of the IQR for sample medians when the sample size is 30 is approximately of the width of the population IQR
WIDTH 0.507 kg-ish(67 mm)
WIDTH 0.095 kg-ish(11 mm)
1/5
Q4: I notice that the width of the IQR for sample medians when the sample size is 400 is approximately __________ of the width of the population IQR
WIDTH 0.025 kg-ish(3.5 mm)
WIDTH 0.507 kg-ish(67 mm)
1/20
Q5: Relationship between the width of the IQR for sample medians of sample size n and the population IR and the sample size… IQR for sample medians (sample size = n) is
approximately of the population IQR
When n = 400 the IQR of the sample medians is approximately ________________ of population IQR
When n = 30 the IQR of the sample medians is approximately ________________ of population IQR
n1