Boxplot
Boxplot’s relation to Mean
- Longer tail on the upper side means mean is higher than the median (median is shifted towards LQ) [a +vely skewed distribution]
- Longer tail on the lower side means mean is lower than the median (median is shifted towards UQ) [a -vely skewed distribution]
Minitab Tricks
Importing .dat, .csv, xls file in Minitab
- File -> Open Worksheet [Choose .dat, .csv etc]
Removing empty cells in boxplot for between-subject design
- Double click the axis variable.
- Uncheck: “Include empty cells”.
- This shows only those ticks that has some data in it, which is very useful in case of between-subject design, as the participants are divided into different treatment groups.
Changing order of x-axis groups
Minitab picks a default ordering for x-axis groups (usually Alphabetical or Numeric ordering) If you want to change the order of group variables on x-axis (e.g. Low, Medium, High to Medium, Low, High):
- Select the column in the data window which represents the group in the graph.
- Right click and select Column->Value Order
- Select User-specified order
- Add the desired order, Click OK
- Any graph from now onward will follow that order
Changing color of x-axis groups
- The colors for groups can be selected in the dialog box at Tools->Options->Graphics-> Data View With Groups -> Symbol and Line Colors
- You can also change color for individual groups or sub-groups by double clicking on the bars and choosing appropriate attributes in the dialog box.
- Before double clicking, click just once to switch between different grouping variables.
SEM vs 95% CI
http://www.graphpad.com/articles/errorbars.htm
Notes:
- Assuming unpaired t-test.
- SEM bars are often about half or less smaller than 95% CI bars.
- SEM Bars
- When SEM bars overlap , There is surely no statistical significant difference (p>0.05).
- When SEM bars do not overlap, There may or may not be a statistical significant difference.
- 95% CI bars
- When CI bars overlap, There may or may not be a statistical significant difference.
- When CI bars do not overlap, There is definitely a statistical significant difference (p<0.05).
Letter size paper in pdflatex
Sometimes problem comes from incorrect specification of PDF page height and width.
Put this code after \begin{document}
\special{papersize=8.5in,11in}
\setlength{\pdfpageheight}{\paperheight}
\setlength{\pdfpagewidth}{\paperwidth}
% \hoffset = -0.2truein %moves everything left and right
% \voffset = -0.2truein %moves everything up and down