What is meant by Estimation ?
Estimation (or estimating) is the process of arriving at an estimate, or approximation. The estimate is a certain value that can be used for a specific purpose despite incomplete, rounded off, uncertain, or unstable data as the input.
“Estimating the value of a corresponding population parameter using the value of a statistic derived from a sample” is what estimation entails, and surely a complex definition of estimation, especially in statistics. Usually, in simpler terms, when we estimate the measurement of certain objects, we use units like yards, inches, meters, feet, etc. and assume the value or magnitude of a particular object or thing.
For example, before building a house, we always make an estimate of the structure of the building.
How is an Estimation different from a Measurement ?
An estimation is a knowledgeable prediction of how far (distance) or how long (length) something is, or how many things will fit in a jar, for that matter. Through estimation, we assume the approximate amount of things. Measurement, on the other hand, is the technique of determining the quantity of products that exist. For measurement, we use units such as kilograms, kilometers, meters, centimeters, inches, etc.
When do we Estimate and when do we Measure ?
In everyday life, we estimate a lot of things, sometimes without even realising it!
For example, we do not look at the watch each time we need to tell someone what time it is. Usually, we look at the watch just once. Post that, we guess the time by approximation. The act of counting the stars is another classic example of approximation.
Unlike estimation, measurement is necessary when we choose something for a particular use.
For example, when we need to buy a curtain for a window, it is imperative to first measure the length of the window, and only then can we buy the curtain for that particular window.
Example: the length of the door is 6 feet and the breadth is 3 feet.
What are the Disadvantages Estimation over Measurement?
One of the major disadvantages of estimation is that it is uncertain. For example, if we are working on a project,then, at the end of the project, all estimates are subject to uncertainty. Some of these uncertainties may stem from the project itself and others, from assumptions.
An estimate made at the 8% mark of a project, for example, might be based on lesser-known data than one made at the 45% mark, making it significantly less reliable.
Large, complex projects involving numerous teams are fraught with risk, since one team’s performance does not always translate to the other. The project manager must make assumptions about future performance, and the standard estimate-at-completion formula assumes that project teams do not learn from past mistakes. All these elements contribute towards erroneous estimates.
In mathematics, estimating does not work. To get an exact solution, we can’t estimate the results of a problem. We just need correct data, which is called measurement.
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Solved Examples
Example 1: How can we measure the length of the eraser?
Solution: We can measure the length of the eraser using a ruler as shown in the figure below.
Hence, the length of the eraser is approximately 3 cm.
Example 2: A bunch of celery is about 8 cm long. Draw a carrot that is about 5 cm long.
Solution: Going by the length of this bunch of celery, we can estimate the length of the carrot. Thus, we will be able to draw a 5-centimeter long carrot as shown below:
Example 3: The rope in the figure below is about 7 inches long. What can be the best estimate of the length of the battery?
Solution: As we can observe, the battery is shorter than the rope and is approximately half the length of the rope. So, the length of the battery is approximately 4 inches.
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We measure the length of a car in meters because when the length of an object is shorter, we usually use the meters or feet as the unit of measurement.
Customary units measure length and distance in yards, inches, centimeters, miles, and meters.