UNIT 1: MEASUREMENT AND PROBABILITY

Math 3202

Accuracy and Precision

Accuracy is the degree to which a measurment is measured and reported correctly

Precision is the degree of exactness to which a measurement is expressed. It depends on the scale of the instrument used.

Accuracy and Precision This angle could be read as 46.5, 47, or

even 48. These are all accurate measurements, but they vary in precision.

Accuracy and Precision NOTE: Be careful about units!!!

One very common measuring error is to measure something properly but state the measurement in the wrong units.

For example a door is about 60 inches wide, if you said it was 60 feet wide you would be way off!!!!

Accuracy and Precision Explore Accuracy and Precision on page 7

of the text.

A & P: On the Job 1 (pg 8) Vic and his son are going to pour a

concrete pad before building a shed. They want the pad to be 12 ft long, 8 ft wide, and 4 in thick.

Vic’s son wants to calcuate the volume of the concerete needed. He knowns that:Volume = Length x Width x Height (or thickness).

So he thinks: V = lwh V = 12 x 8 x 4 V = 392.

A & P: On the Job 1 (pg 8) Vic’s Son says: “We need 392 cubic feet

of concrete” Vic says, “No way, we only neeed 32

cubic feet”

A & P: On the Job 1 (pg 8)Question

a) Whose calculation is accurate? Explain

b) Is it important for this calculation to be accurate? Explain.

A & P: On the Job 1 (pg 8)Your Turn:

Calculate the volume of concrete needed for a pad that measures 20 ft by 10 ft by 6 in.

Accuracy and Precision Check Your Understanding on page 9 &

10

A & P: On the Job 2 Greg is redecorating a bedroom in his

house. He knows that his measurements need to be accurate, but the degree of precision required depends on the job.

A & P: On the Job 2 A) Greg wants to determine how much

paint to buy. The dimensions of the room are 12’ 8 “ by 10’ 10”. The ceiling is 7’ 10 “ high. What degree of precision does he need for the room’s measurements? How much paint should he buy?

A & P: On the Job 2 B) Greg is also replacing the door and

window casing. The door frame measures 80” by 30”. The door casing will be installed so that about ” of the door frame is exposed. Greg needs to cut the pieces of casing.

What degree of precision downs he need for the measurements? How long should he cut the pieces of casing?

A & P: On the Job 2 Your Turn

A) A second bedroom in Greg’s house has dimensions that are 10 ‘ 4 “ by 13 ‘ 10 “. The ceiling is 7’ 10½ “ high. He wants to paint the bedroom, how much paint should he buy?

B) A closet door in the bedroom is 80” high and 24” wide. Determine the length he should cut the horizontal piece of casing that goes across the top of the closet door frame.

Accuracy and Precision Check Your Understanding on page 13-

14

Accuracy and Precision Tolerance is the total amount that a

measurement is allowed to vary.

For example, a piece of lumber is sold as an 8 foot length with a tolerance of ± inch. This means that some of the boards may be 7 ft in length, and some may be 8 ft in length.

A&P: On the Job 3 A clothing manufacturer seems men’s

pants. Men’s pants are measured in whole-inch sizes by their waist measurement and, often, by their inseam measurement as well. The company allows for a tolerance of ± ¼ “ when labelling their products.

A&P: On the Job 3 A) What is the tolerance in the waits

measurement of a pair of pants?

B) What are the maximumand minimum allowablewaist and measurementsthat can be labeled as 32 inch waist pants?

A&P: On the Job 3 The same manufacturer allows a

tolerance for the neck measurement of a men’s shirt of ± ”. Their men’s shirts are sold in ½ “ increments of the neck measurement, for example, 14½”, 15”, 15½”, 16” and so on.

A&P: On the Job 3 A) What is the tolerance for the neck

measurement of a men’s shirt?

B) What are the maximum and minimum allowable measurements that can be sold as a men’s shirt with a 15” neck?

Accuracy and Precision Check Your Understanding on page 16-17

Accuracy and Precision Work With It: Page 18-19