Can You Solve Amazon’s Hanging Cable Interview Question?
THAT'S A MOST IMPORTNT AMAZON INTERVIEW QUESTION WHICH MOSTLY ASKED IN INTERVIEW:
A cable of 80 meters (m) is hanging from the top of two poles that are both 50 m from the ground. What is the distance between the two poles, to one decimal place, if the center of the cable is:
(a) 20 m above the ground? (b) 10 m above the ground?
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GENERAL CATENARY EQUATION IS:
Y = a Cosh(x/a) - a
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Arrangement of data according to time period is called as Time Series.
OR
Cronological arrangement of data is defined as Time Series.
What are the Components of Time Series?
REASONS:
Reasons of fluctuations (Ups and Downs) in Time Series are the components of time series.
COMPONENTS OF TIME SERIES:
There are Four Components of Time Series:
1 - Secular Variations (Trend)
2 - Seasonal Variations
3 - Cyclic Variations
4 - Irregular Variations
What are the Secular Variations?
The Variations which are very long term and which may covers more than 10 years to occur are known as Secular Variations. These are slow and gradual changes.
REAL LIFE EXAMPLE:
The transport system in old time is converted into the modern transport system and it took very long time to change.
What are the Seasonal Variations?
The Variations which are caused by Seasons, Religious festivals and our Traditions are called as Seasonal Variations. These changes reoccur after the fix interval of time.
EXAMPLE:
Great demand of warm clothes near winter.
What are the Cyclic Variations?
The Variations which are long term oscillations and which are like swings or waves type movements are called as Cyclic Variations.
Most Important Real Life Example:
The main example of Cyclic Variations is the life of a business man.
There are four Stages in the life of a business man:
1 - Prosperity
2 - Contraction (Recession)
3 - Depression (Trough)
4 - Recovery
What are the Irregular Variations?
The Variations which are due to accidental events or random events like floods, earthquakes, famines, wars.
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Difference between Multiple Correlation Coefficient and Partial Correlation Coefficient:
MULTIPLE CORRELATION:
Multiple Correlation is the relationship between a Variable and a Combined Variable.
MULTPLE CORRELATION COEFFICIENT:
The Coefficient of a Multiple Correlation measures the degree of relationship between a variable and its estimate from the regression equation.
REPRESENTATION:
It is represented as...
FORMULA:
PARTIAL CORRELATION:
The relationship between any two variables by neglecting the effect of other variable is called as Partial Correlation.
PARTIAL CORRELATION COEFFICIENT:
The coefficient of a partial correlation measures the degree of linear relationship between any two variables in a multivariate problem under the condition that any common relationship with all other variables has been removed.
REPRESENTAION:
It is represented as...
FORMULA:
NOTE:
We know that
r XY is...
then r12 will be as...
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1 - Correlation Coefficient 'r' lies between - 1 and + 1 , that is; - 1 < r < + 1 .
2 - Correlation Coefficient 'r' is Symmetric about X and Y....
r XY = r YX
The Formula of Correlation Coefficient ' r ' is.....
3 - Correlation Coefficient ' r ' is the Geometric Mean of two Regression Coefficients.
REGRESSION COEFFICIENTS:
There are Two regression coefficients :
b YX;
b XY;
NOTE: The Main Common formulas of Regression Coefficients are:
b YX;
b XY;
4 - Correlation Coefficient 'r' in Independent of change of origin and scale, that is;
r XY = r UV
But the Formula of " r UV " is:
5 - Correlation Coefficient 'r' is the Independent of any unit of measurement.
MOST IMPORTANT POINTS:
The Regression line Y on X is...
The Regression line X on Y is...
At last,
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QUESTIONS WITH ANSWERS: Simple & Easiest with Real life Examples 2021
What is Correlation?
Relationship between two Variables is called as Correlation.
For Example, We can say Married Persons " Relationship between Husband and Wife ".
What is Correlated?
The movement of one variable is accompanied by the movement of other variable is called as Correlated.
For Example, Let's take an example of Cars; We have Two Cars, We bind the One Car with the other Car by a rope then you can noticed that When One Car will move then automatically other car will move. That's relation is CORRELATED. It is denoted by " r ".
What is the Difference between Positive Correlation and Negative Correlation?
STEP-BY-STEP:
What is Positive Correlation?
When movement of two variables is in same direction that is both variables may increase or both decrease is called as Positive Correlation.
For Example, let's suppose that two persons have own bikes and they are racing in same direction then obviously both persons speed may increase or decrease. That's is a Positive Correlation.
NOTE: The value of 'r' will be positive When r = + 1, Correlation is perfect positive.
What is Negative Correlation?
When movement of two variables are in opposite direction then Correlation will be negative.
For Example, let's suppose there are two persons; One is going to the right side and other is going to the left side which shows that they have not any relationship. So, correlation will be negative.
NOTE: The value of 'r' will be negative When r = - 1, Correlation is perfect negative.
What is Correlation Coefficient or Coefficient of Correlation?
The Strength of relationship between two variables is measured by the formula which is named as Correlation Coefficient. It is denoted by 'r'.
General Formula:
Where
Co-variance of X and Y formula is:
Variance of X and Y formula is:
Now, at last..
Common Formula:
That's common formula is a main formula which we use in calculation of 'r'.
What is Rank Correlation?
When actual values of two variables are ranked according to some common characteristics then Correlation will be Rank Correlation.
What is the Coefficient of Rank Correlation?
The Coefficient of Rank Correlation is:
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I have discussed here theory of REGRESSION STEP-BY-STEP with #secrets #shortcuts #concepts which nobody tells you about that.!
SEQUENCE: REGRESSION; REGRESSION EQUATION; REGRESSOR; REGRESSAND; EXACT RELATIONSHIP; INEXACT RELATIONSHIP; STANDARD ERROR OF ESTIMATE OF REGRESSION(STANDARD DEVIATION OF REGRESSION).
QUESTIONS WITH ANSWERS:
WHAT IS REGRESSION?
Dependence of One Variable on other Independent Variable is called as REGRESSION.
WHAT IS REGRESSION EQUATION?
An Equation which estimates the value of Dependent Variable with the help of Independent Variable by knowing the values of unknown parameters is called as REGRESSION EQUATION.
REGRESSION EQUATION
Y on X X on Y
Y = a + b X X = a + b Y
Y is Dependent Variable, X is Dependent Variable
X is Independent Variable, Y is Independent Variable
WHAT IS THE DIFFERENCE BETWEEN REGRESSOR AND REGRESSAND?
WHAT IS THE DIFFERENCE BETWEEN PREDICTOR AND PREDICTAND?
WHAT IS THE DIFFERENCE BETWEEN EXPLANATORY VARIABLE AND EXPLAINED VARIABLE?
The Independent Variable is called as REGRESSOR or PREDICTOR or EXPLANATORY VARIABLE.
The Dependent Variable is called as REGRESSAND or PREDICTAND or EXPLAINED VARIABLE.
WHAT IS THE DIFFERENCE BETWEEN EXACT RELATIONSHIP AND INEXACT RELATIONSHIP?
WHAT IS THE DIFFERENCE BETWEEN MATHEMATICAL RELATIONSHIP AND PROBABILISTIC RELATIONSHIP & ESTIMATED RELATIONSHIP?
Exact Relationship or Mathematical Relationship:
A Relationship which calculates the value of one Variable Exactly with the help of other Variable is called as Estimated Relationship or Mathematical Relationship.
For Example,
Inexact Relationship or Probabilistic Relationship or Estimated Relationship:
A Relationship which estimates the value of one Variable (Dependent Variable) with the help of other Variable (Independent Variable) is called as Inexact Relationship or Probabilistic Relationship or Estimated Relationship.
For Example, The Relationship between Age and Weight.
DEFINE STANDARD DEVIATION OF REGRESSION or STANDARD ERROR OF ESTIMATE OF REGRESSION?
Positive Square Root of Mean of Squared Deviation from Estimated Trend Values from Regression Equation is called as Standard Deviation of Regression or Standard Estimate for Regression.
For Y on X Y = a + b X
&
For X on Y X = a + b Y
&
Most Important Point;
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2- The Process of analysing the total variation in the dependent variable Y into its components; one explained by regression line and the other residual or unexplained part is defined as: ?
(A) Analysis of Variance for Regression (B) ANCOVA
Option (A) is correct.
3- Total SS(Sum of Squares) =: ?
(A) Within SS + Between SS (B) Residual or Error SS(SSE) + Regression SS(SSR)
Option (B) is correct.
4- In ANOVA for Multiple Regression and Testing Hypothesis about the "beta" parameters, degrees of freedom are: ?
(A) V1 = 2, V2 = n - 3 (B) V1 = k - 1, V2= n - k
Option (A) is correct.
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1- Experimental Design means _ used to collect the data: ?
(A) Plan (B) Designing
Option (A) is correct.
2- The Purpose of randomization is to _ bias and other sources of extraneous variation: ?
(A) Accept (B) Remove
Option (B) is correct.
3- A term reffering to the amount of balancing, blocking and grouping of the experimental units is called as: ?
(A) Local Control (B) Replication
Option (A) is correct.
4- A Completely Randomized Design (CR) design is also called as: ?
(A) One-Way ANOVA (B) Two-way ANOVA
Option (A) is correct.
5- A Randomized Complete Block Design (RCB) is also defined as: ?
(A) Two-Way ANOVA (B) One-Way ANOVA
Option (A) is correct.
6- A Replication is used to secure more accurate estimate of the _ : ?
(A) Repetition (B) Experimental Error
Option (B) is correct.
7- A Replication is used to _ the experimental error and thereby to increase precision: ?
(A) Increase (B) Decrease
Option (B) is correct.
8- A Completely Randomized (CR) design is one in which treatments are assigned to experimental units completely _ : ?
(A) At Random (B) At Most
Option (A) is correct.
9- In CR Design, There is possibility of entering the whole of the variation among the experimental units into the _ as the randomization is not restricted in any direction: ?
Note: You already know that ' Y = a + b X ' is also a Regression line.
2- The Equation of Hyperbola is: ?
(A) 1/B = X (B) 1/Y = a + b X
Option (B) is correct.
3- We fit an Exponential Curve If the first differences of the Logarithms are approximately: ?
(A) Constant (B) Variable
Option (A) is correct.
4- For better the Fit, The Sum of Squares must be: ?
(A) Bigger (B) Smaller
Option (B) is correct.
5- Non-Linear Form is: ?
(A) 1/Y = a + b/1 + X (B) Y = a + b X
Option (A) is correct.
6- Logistic Curve has _ different Stages: ?
(A) 4 (B) 3
Option (A) is correct.
Note: Must focus on that's, Logistic Curve has Stages; 1- Period of relatively slow growth, 2- Period of accelerated growth, 3- Period of Decelerated growth, 4- Period of Stability.
7- We Fit a Reciprocal line 1/Y = a + b X, If the reciprocals of data show a _ when plotted in a graph: ?
(A) Regression line (B) Straight line
Option (B) is correct.
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1- Dependence of one Variable on other Independent Variable is called as: ?
(A) Regression (B) Correlation
Option (A) is correct.
Note: Y = a + bX is a Regression Line. Must remember that 'Y' is a Dependent Variable and 'X' is an Independent Variable. Next, 'a' and 'b' are Least-Squares Estimates.
2- The Independent Variable is called as: ?
(A) Regressand (B) Regressor
Option (B) is correct.
3- Regressand is also called as: ?
(A) Predictand (B) Predictor
Option (A) is correct.
Note: Must note that's points......
Dependent Variable is called as Regressand, Predictand, Explained Variable. But, Independent Variable is called as Regressor, Predictor, Explanatory Variable.
4- A distribution for which probability is same for each value of success is called as: ?
(A) Bernoulli's Distribution (B) Uniform Distribution
Option (B) is correct.
5- The Function of Uniform Distribution is: ?
(A) P(X) = 1/k (B) P(X) = k
Option (A) is correct.
6- In Sequence, 1 + 2 + 3 +.....+ n =: ?
(A) n/2 (B) n(n+1)/2
Option (B) is correct.
7- The Mean of Uniform Distribution is: ?
(A) k + 1/2 (B) k/2
Option (A) is correct.
8- Poisson Distribution and Normal Distribution are the Limiting Functions of: ?
(A) Binomial Distribution (B) Bernoulli's Distribution
Option (A) is correct.
9- Standard Normal Variable 'Z' is equal to: ?
(A) X/sigma (B) X - Mean/sigma
Option (B) is correct.
10- Normal Distribution has range from: ?
(A) - infinity to + infinity (B) 0 to infinity
Option (A) is correct.
11- Mean Deviation of Normal Distribution is: ?
(A) 4/5 sigma or 0.7979 sigma (B) 2/3 sigma or 0.6745 sigma
Option (A) is correct.
Note: Must remember that Quartile Deviation of Normal Distribution is 2/3 sigma or 0.6745 sigma.
12- The Total Area under Normal Curve is always: ?
(A) 2 (B) 1
Option (B) is correct.
Note: Many people ask that how can we explain " Total area under normal curve is 1".?
Very easy and simple answer : 0.5 + 0.5 = 1.
13- The Shape of Normal Distribution is: ?
(A) Bell Shaped (B) Square Shaped
Option (A) is correct.
14- Percentage area between Mean - sigma and Mean + sigma is: ?
(A) 95.45 % (B) 68.67 %
Option (B) is correct.
Note: But, Percentage area between Mean - 2 sigma and Mean + 2 sigma is 95.45 %. And, Percentage area between Mean - 3 sigma and Mean + 3 sigma is 99.73 %.
15- When sample size "n" is very large and neither "p" nor "q" is very small, that's called as: ?
(A) Normal Distribution (B Poisson Distribution
Option (A) is correct.
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Note: But, all Trials are Dependent in Hypergeometric Experiment.
2- In Binomial Experiment, drawing is done: ?
(A) With Replacement (B) Without Replacement
Option (A) is correct.
Note: But, In Hypergeometric Experiment, drawing is done Without Replacement.
3- Binomial Distribution has range from: ?
(A) 0,1,2,.....infinity (B) 0,1,2,......n
Option (B) is correct.
Note: Must remember that also Hypergeometric Distribution has range from 0,1,2,......n.
4- The Probability of failure 'q' is equal to: ?
(A) 1- p (B) 1-q
Option (A) is correct.
5- The Variance of Binomial Distribution is: ?
(A) npq (B) np
Option (A) is correct.
Note: But, In Binomial Distribution, Mean = np.
6- For Negative Binomial Distribution, Mean and Variance have a relation: ?
(A) Mean > Variance (B) Mean < Variance
Option (B) is correct.
Note: Must focus on that's, In Binomial Distribution, always Mean > Variance.
7- The Mean of Hypergeometric Probability Distribution is: ?
(A) nk/N (B) npq
Option (A) is correct.
8- In Hypergeometric Probability Distribution, Probability 'p' is equal to : ?
(A) k/N (B) k/n
Option (A) is correct.
Note: Attention!!
Now, I am going to tell you most Important points which nobody tells you about that. Must remember that In sense of Problems solving, In case of With Replacement , always use the formula of Binomial Distribution. But, In case of Without Replacement , always use the formula of Hypergeometric Distribution.
9- If 'n' becomes very large and the probability of success "p" is very small, then that's type of Distribution is defined as: ?
(A) Normal Distribution (B) Poisson Distribution
Option (B) is correct.
Note : For example, in problems solving,, n=500 and p=0.01. then we always use Poisson Distribution.
10- In Poisson Distribution, Mean and Variance have a relation: ?
(A) Mean = Variance (B) Mean < Variance
Option (A) is correct.
Note: Must remember that In Poisson Distribution, Mean = np and Variance = np.
11- The Product of N and P(X) ; NP(X) is equal to: ?
(A) Expected Frequency (B) Observed Frequency
Option (A) is correct.
12- In Poisson Process, Average number of occurances per unit time is equal to: ?
(A) Lemda (B) t
Option (A) is correct.
Note: t shows 'time interval".
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