In semiconductor manufacturing, wet chemical etching is often used to remove silicon from the backs of wafers prior to metalization. the etch rate is an important characteristic in this process and known to follow a normal distribution. two different etching solutions have been compared, using two random samples of 10 wafers for each solution. assume the variances are equal. the etch rates are as follows (in mils per minute): solution 1 solution 2 9.7 10.6 10.5 10.3 9.4 10.3 10.6 10.2 9.3 10.0 10.7 10.7 9.6 10.3 10.4 10.4 10.2 10.1 10.5 10.3 calculate sample means of solution 1 and solution 2

Sample mean for solution 1:  19.27; sample mean for solution 2:  10.32

Step-by-step explanation:

To find the sample mean, find the sum of the data values and divide by the sample size.

For solution 1, the sum is given by:

9.7+10.5+9.4+10.6+9.3+10.7+9.6+10.4+10.2+10.5 = 192.7

The sample size is 10; this gives us

192.7/10 = 19.27

For solution 2, the sum is given by:

10.6+10.3+10.3+10.2+10.0+10.7+10.3+10.4+10.1+10.3 = 103.2

The sample size is 10, this gives us

103.2/10 = 10.32

2 over 5

step-by-step explanation:

the 2: 3 ratio is the length of the ac segment to the cb segment total length. this implies that the ratio between segment ac length and segment ab length is 2: 5. point c is 2/5 from a to b, so the required fraction is 2/5.