# Suppose the Office of Institutional Research and Planning (IRP) calls 50 recent alumni and ask about their current income. The average reported monthly.

## Presentation on theme: "Suppose the Office of Institutional Research and Planning (IRP) calls 50 recent alumni and ask about their current income. The average reported monthly."— Presentation transcript:

Suppose the Office of Institutional Research and Planning (IRP) calls 50 recent alumni and ask about their current income. The average reported monthly income of these 50 alumni was \$3,100.

Question: The 50 surveyed students are a_____. A.Parameter B.Population C.Sample D.Statistic

Question: “average income of \$3,100” is a _______? A.Parameter B.Population C.Sample D.Statistic

What would need to change with regards to the sample size, n, to make the “reported average income” a parameter? A.n=1 B.n=1,000 C.n=Number of recent alumni=N D.You can’t find the parameter value because the population is infinite in size.

A parameter describes a characteristic of the population. We typically can’t sample the entire population (do a census), so we collect a sample. We design our sample so it is likely representative of the population. A statistic is calculated from a sample. We use the statistic to estimate the parameter.

Very first steps Define your population Determine what parameter of the population is of interest to you. (What’s the study’s question?)

A prospective cohort study of over 1,300 children found that children who are breast- fed for a year, on average, test 4 IQ points higher than non breast-fed children. (JAMA 7/29/2013)

Question: Not knowing more details about this study, this study could most likely be classified as an____________. A.observational study. B.experiment.

Question: To use simple random sampling to sample 10 people from this class of 80, I should: A.Use every 8 th name from my roll sheet. B.Have people write their names on a piece of paper, put them in a hat, and pull 10 pieces of paper from the hat. C.Ask for 10 volunteers. D.Assign each person a number (1-80) and then use a computer or random number table to get 10 names.

Why use randomness when sampling? Avoid bias!

Download ppt "Suppose the Office of Institutional Research and Planning (IRP) calls 50 recent alumni and ask about their current income. The average reported monthly."

Similar presentations