Write the real limits for the following scores:
(a) A score of 52;measurement is to the nearest digit.
(b) 800 yd.; measurement is to the nearest 100 yd.
(c) 460 lb.; measurement is to the nearest 10 lb.
(d) .6 in.; measurement is to the nearest .1 in.
(e) .47 sec.; measurement is to the nearest .01 sec.
The Correct Answer and Explanation is:
Answers: Real Limits for Given Scores
Real limits represent the boundaries of a measurement, accounting for the precision with which it was taken. For each case, the real limits are found by subtracting and adding half of the unit of measurement from the recorded value.
(a) A score of 52; measurement is to the nearest digit (1)
- Real limits: 51.5 to 52.5
(b) 800 yd.; measurement is to the nearest 100 yd
- Real limits: 750 to 850 yd
(c) 460 lb.; measurement is to the nearest 10 lb
- Real limits: 455 to 465 lb
(d) 0.6 in.; measurement is to the nearest 0.1 in
- Real limits: 0.55 to 0.65 in
(e) 0.47 sec.; measurement is to the nearest 0.01 sec
- Real limits: 0.465 to 0.475 sec
Explanation
In statistics and measurement theory, a real limit (also called a class limit or measurement boundary) refers to the actual range that a measurement represents. Every numerical measurement, even if it appears exact, includes a degree of approximation due to the limits of the measuring instrument. This approximation is often expressed as being “to the nearest unit,” such as nearest whole number, tenth, or hundredth.
To find the real limits, we account for this uncertainty by using ± 0.5 of the smallest unit used in measurement. For example, if a weight is recorded as 460 lb to the nearest 10 lb, it means the actual weight could be as low as 455 lb and as high as just under 465 lb — so the real limits are from 455 to 465 lb.
This approach is critical in interval and ratio level data, where we interpret measurements as being part of a continuous scale. Real limits are especially important when constructing frequency distributions, histograms, or when applying certain statistical tests where class intervals or continuous variables are involved.
By calculating real limits, we ensure that our interpretation of the data accounts for the imprecision inherent in measurement tools. Ignoring real limits can lead to misinterpretation, particularly in finely tuned scientific or statistical analyses. Thus, understanding and applying real limits allows for more accurate and valid representation of data in both academic and professional research contexts.
