Zach’s facts have been extracted from the book to remind you of the key concepts you and Zach have learned in each chapter.

Zach's Facts 2.1 Writing up research

• Scientists use a standard article format for reporting the research that they do.
   
• Although you will find variations on this format, there is usually a summary at the beginning (abstract), then sections explaining (1) past research and why the current study has been done (introduction); (2) how the research was done (methods); (3) the analysis and what was found (results); and (4) the implications of the results for theory and practice, and any important limitations and remaining gaps in our knowledge (discussion).
   
• Scientists always back up what they say with reference to published work, so you will see references within the report that are collected together into a references section at the end.
   

Zach's Facts 2.2 Statistical notation

• Do calculations and solve equations using BODMAS/PEMDAS, which stands for Brackets/Parentheses, Order/Exponents (in other words ‘to the power of’), Multiplication and Division, then Addition and Subtraction.
   
• y usually denotes an outcome variable (a dependent variable), and x a predictor variable (which can be an independent variable). However, x is also used to denote the scores you have collected.
   
• means ‘add everything up after the symbol’.
   

Zach's Facts 2.3 Variables and measurement

• Variables can be discrete (can only take on certain values) and continuous (can take on any value).
   
• Variables can be measured on different scales of measurement:

• Nominal scale: Names are given to differentiate distinct categories (e.g., whether someone works as a scientist, musician, or counsellor).
   
• Ordinal scale: The same as a nominal scale, but the categories have a logical order (e.g., whether people get a grade D, C, B or A on a college course).
   
• Interval scale: Equal intervals on the variable represent equal differences in the property being measured (e.g., the difference between 6 and 8 is equivalent to the difference between 13 and 15).
   
• Ratio scale: The same as an interval scale, but there is a meaningful zero representing a complete absence of the construct being measured. The ratios of scores on the scale will make sense (e.g., a drummer playing at 200 beats per minute is, in reality, playing twice as fast as a drummer playing at 100 beats per minute, and a drummer playing at 0 beats per minute isn’t playing at all).
   

Zach's Facts 2.4 Measurement issues

• Measurement error is the difference between the numbers used to represent the thing that we’re measuring and the actual value of the thing we’re measuring.
   
• The validity of a questionnaire or instrument is whether it measures what it sets out to measure.
   
• The reliability of a questionnaire or instrument is whether it can be interpreted consistently across different situations