ISI
Lab 2

1: Introduction 2: Background 3: Explore data 4: Draw inferences 5: Simulation 6: Standard error 7: Central Limit Theorem 8: Theory-based 9: Conclusions 10: Follow-up 11: Summary

Step 3. Explore the data

Open the Excel file from your instructor to see your class data.

First we will look at a graph and numerical summaries of the sample data. Press the link below to view technology instructions for the Descriptive Statistics applet.

Click here to display applet instructions (Descriptive Statistics)

Choose Analyze > Distribution. JMP will recognize that you have a quantitative variable and produce a histogram instead of a bar graph. Click on SleepHrs and then click on Y, Columns to enter the variable into that box. Press OK. Click the SleepHrs pull-down menu and select Display Options > Horizontal Layout. If you put your mouse below the horizontal scale (to show a hand) and then right click, select Add Axis Label to specify the variable description. (Press OK when done.) JMP also produces lots of numerical summaries (statistics) for this quantitative variable.

In the Excel file, click on the A to highlight all of the A column. Copy this to your clipboard (e.g., ctrl-C). In the applet, press the Clear button. Click in the Sample Data box and paste the data (e.g, ctrl-V). Press Use Data. Check the Actual boxes for the Mean and the Std. Deviation

(e) Include a copy of this output in your report (remember to make sure you have a title AND an axis label!).

(f) Write a paragraph summarizing the distribution of the sleep time responses in this sample:

You should identify the variable (context), the sample size, describe the shape (e.g., roughly symmetric or skewed to the right or skewed to the left?), report the sample mean (including a suitable symbol and measurement units), and report the sample standard deviation (including a suitable symbol and measurement units). Also make sure you discuss any unusual observations or outliers (1 or 2 individual observations that don't follow the general pattern).

Also comment on whether the data support the research conjecture that students at your school average less than 8 hours of sleep on a typical night (i.e., is the sample mean in the "right" direction)?