1. A new, lightweight plastic will be used in making cell phone screens. Its ten
ID: 3304758 • Letter: 1
Question
1. A new, lightweight plastic will be used in making cell phone screens. Its tensile strength measurements are known to have normal distribution with mean 33.1 and variance .412. a) what is the value of tensile strength which is greater than 20% of measurements and less than 80% of measurements? b) If a simple random sample of size 50 is to be collected, how likely would it be that the sample mean is observed to be 32.9 or less? Explain 2. Audio CD's require a special coating to prevent scratching; the harder the coating the better to prevent scratching. Three types of coatings are tested for hardness and the results are illustrated in the box plots shown below. There are 40 observations in each group. Type-C t Type-B Type-A 2.90 2.95 3.00 3.05 3.10 3.15 3.20 Hardness Compare basic features of the distributions of the three coatings on the basis of these plots. Which coating, if any, should be recommended and why?Explanation / Answer
2) The harder the coating , better the CD. so we really need to read the boxplot wellhere.
Boxplot basically tells us the median value (black center line) along with the extreme ends (known as whiskers )
For type C , the median value is highest however , the length of the whiskers on the lower side extends utp 2.97 .
For type B , the median value is quite close to type C , at the same time the extreme lower end of the hardness is quite low 3.07(approx) , this tells us that the lower end of the hardness for type b is 3.07 , which is quite above the lowest end of the type c
For type A , again the value of the lower end goes down upto 2.9 , which means that type a is not suitable for making CDs.
Hence the recommendation goes in favor of type B
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