/    /  Statistics – Interview questions Part 2

### 1. What Is Skewness?

Answer: Is a measure of the asymmetry of the data around the sample mean.

If skewness is negative, the data spreads out more to the left of the mean than to the right.

If skewness is positive, the data spreads out more to the right.

Skewness(x) % return-0.5954

### 2. What Is Variance?

Answer: It describes how far values lie from the mean.

var(x) %return 1.1429

### 3. What Is Kurtosis?

Answer: Kurtosis is a measure of how outlier-prone a distribution is.

kurtosis(x) % return2.3594

### 4. What Is Moment?

Answer: A moment is aQuantitative measure of the shape of a set of points.

moment(x, 2); %return second moment

### 5. What Is Covariance?

Answer: A Covariance is nothing but,Measure of how much two variables change together.

y2=[1 3 4 5 6 7 8]

cov(x,y2) %return 2*2 matrix, diagonal represents variance.

### 6. What is the goal of A/B Testing?

Answer: It is a statistical hypothesis testing for a randomized experiment with two variables A and B.

It is used to identify any changes to the web page to maximize or increase the outcome of an interest. A/B testing is a fantastic method for figuring out the best online promotional and marketing strategies for your business. Hence, it can be used to test everything from website copy to sales emails to search ads

### 7. What do you understand by statistical power of sensitivity and how do you calculate it?

Answer: Sensitivity is commonly used to validate the accuracy of a classifier (Logistic, SVM, Random Forest etc.).In simple terms it is nothing but Predicted True events/ Total events. True events are the events which are true and model also predicted them as true.