Basics of ML & AL Week 2 Challenge

2nd question answer:

Significance of Expected value:

Actually the output results of both "Mean" and "Expected value" gives the average value of the Random variable. But the "Mean" is used only when probabilities of all the experiments are equal. But we can use the Expected value for both different probabilities as well as the same probabilities of experiments. But for convenience, we mostly prefer the Expected value for different probability cases.

3rd question & answer:

Having skewness in the curve considered to be bad in the analysis......?

Having skewness in the curve neither good nor bad in the analysis because it depends on the application.

Suppose, In a company which sells the cars... in this company need negative skewness which indicates the more sales of the cars but in another case like salary appraisal in the company should follow normal distribution which means no skewness is good.

4th question & answer:

4)Evaluate the probabilities for continuous normal distribution with given mean = 680 and standard deviation = 31

ANS:

Given: μ=680, σ=31

a)P(X<711)

z=(x−μ)/σ=(711-680)/31=1......z=1.

so the area under the curve up to z=1 gives the P(X<711).

from the z-chart,

P(X<711)=P(z<1)=0.8413.

b)P(X>740)

z=(740-680)/31=1.9354=1.94

P(z>1.94)=1-P(z<1.94)=1-0.9738=0.0262

P(X>740)=0.0262

c)P(600<x<720)

z1=(600-680)/31=-2.58, z2=(720-680)/31=1.29

area between z1 and z2 from the chart:

z2-z1=0.9075-0.0049=0.9026.

P(600<x<720)=0.9026.

d)P(X=720)

the area under this value is equal to zero.

So P(X=720)=0.

5th question answer:

The graph is called a normal distribution curve which represents the continuous probability distribution. This curve is symmetrical about its mean.in this mean=mode=median.

the area under the curve represents the probability. Most of the data is a cluster around the mean. The tails of the curve never touch the X-axis.

this also scaled to standard normal distribution where mean=0 and standard deviation=1,in which curve the area under the curve between -1 to 1 gives 68.2%.and also -1 to 1 gives 95.4%