Aquality control chart is used to monitor the customer wait time at a local call center. sample means of five times are averaged and plotted over time. the last 50 sample means are randomly distributed between the upper and lower control limits. the process is

in-control

Step-by-step explanation:

basically, their are 2 types of control charts delineated:

1) uni-variate control chart : shows one quality characteristic

2)multivariate control chart : shows 2 or more than two quality         characteristics

in statistics, we have "upper control limit" and "lower control limit".

if the system/variables are within these limits it is 'in-control' other wise 'out of control'

in-control says that all dots are within control limit and they have random pattern.

a 4/6 = 9/12   not proportional

step-by-step explanation:

to find which are not proportional, we can use cross products

if it is true, they are proportional.   if it is not true, they are not proportional.

a 4/6 = 9/12

4* 12 = 6*9

48 = 54

not this is not proportional  

b 2/3 = 12/18  

2* 18 = 3 * 12

36 = 36

this is proportional

c 5/4 = 10/8  

5*8 = 4*10

40 = 40

this is proportional

d 7/5 = 35/25

7*25 = 5 * 35

175 = 175

is proportional

step-by-step explanation: