Description
midpoint = lower/2+upper/2; reversed = lower+(upper-score).
Numeric score transformations can reverse a scale, map anchors or change its mean and standard deviation. Such arithmetic does not establish equal category spacing, comparable constructs or statistical equating between assessments.
midpoint = lower/2+upper/2; reversed = lower+(upper-score).
When to use this tool
Use Scale Reverse Item Midpoint when checking an explicit scale or anchor transformation.
How to use the tool and how it works
- Enter score, lower, upper. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read midpoint, reversed. Use the output convention below.
Require lower <= score <= upper. midpoint = lower/2+upper/2; reversed = lower+(upper-score).1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| score | Score | Required. Finite number. |
| lower | Lower bound under the stated coordinate, derivative or uncertainty convention. | Required. Finite number. |
| upper | Upper bound under the stated coordinate, derivative or uncertainty convention. | Required. Finite number. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| midpoint | Midpoint | Required. Finite number. |
| reversed | Reversed | Required. Finite number. |
{
"input": {
"score": 2,
"lower": 1,
"upper": 5
},
"output": {
"midpoint": 3,
"reversed": 4
}
}Limitations and assumptions
- This reverses one bounded numeric scale. Response categories, reverse-key applicability, psychometric equivalence and scoring validity are not established.
- Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Use appropriate measurement validation or equating methods before treating transformed scales as interchangeable.
References
Similar or alternative tools
- Scale Direction Reversal Flag
When reverse is true return lower+upper-value, otherwise preserve value; reversed echoes the flag.
- Teacher Rating Scale Width
width = upper-lower; intervals = width/step; aligned = Number.isInteger(intervals).