Frequency curve
Topic: Economic Data: Census, NSS, Surveys and Statistical Tools · NCERT: Class 11, Ch 3 "Organisation of Data"; Class 11, Ch 4 "Presentation of Data"; Class 11, Ch 8 "Use of Statistical Tools"
Meaning
A frequency curve is a graph of a frequency distribution drawn as a smooth freehand line. Class marks go on the X-axis and frequencies on the Y-axis. First the points of the frequency polygon are plotted. The curve is then drawn smoothly close to those points instead of joining them with straight lines. It shows the overall shape of a distribution, for example whether it is symmetric or skewed.
Example
For NCERT's daily wages of 85 earners, first draw a histogram. Next, mark the midpoints of the tops of its bars. Then draw a smooth curve close to those points. The curve shows where most wages cluster.
Don't confuse with
- Frequency polygon: joins the same midpoints with straight lines and closes at zero-frequency classes at each end.
- Ogive: plots cumulative frequency, not simple frequency.
Related concepts
- Raw data
- Classification
- Chronological classification
- Spatial classification
- Qualitative classification
- Quantitative classification
- Attribute
- Continuous variable
- Discrete variable
- Frequency