Top Statistics Interview Questions to Help You Prepare

Statistics interview questions for freshers

Statistics interview questions for freshers focus on basic statistics. They evaluate how well you grasp the basic concepts, much like those taught in statistics courses.

1. Explain mean vs. median vs. mode. When should each be used?

2. Explain correlation vs. causation. One of the most commonly asked statistics interview questions by Google.

Correlation—Describes the relationship between two variables. 

Causation—It is a cause-and-effect relationship. In causation, a modification or change in one variable directly leads to a change in the other. Thus, a cause-and-effect relationship.

3. What does "inlier" mean?

An inlier is a data point that is on the same level as the other data points in a dataset. It is often removed because, in most cases, it represents an error instance. An inlier is harder to detect than an outlier and usually requires external data for proper identification.

4. Statistical Six Sigma: What is it?

Six Sigma is a quality management strategy. The model aims to produce error-free results. Standard deviation is denoted by σ. For accuracy and fewer errors, the standard deviation should be kept at a minimum.

Compared to 1σ through 5σ, the Six Sigma model delivers much higher effectiveness. Six sigma ensures the percentage of error-free results produced amounts to 99.99966%.

5. What is your view on "p-value"?

In statistics, the p-value measures the likelihood that the observed effect is not genuine but due to randomness.

A p-value is a step in hypothesis testing.

For example, if the p-value is 0.05 or less than alpha, it means:

- In cases where the p-value is 0.05 or less than alpha, we reject the null hypothesis.
- This indicates that the results are unlikely to have occurred by random chance.
- There is a 5% or lower chance of seeing such extreme results if the null hypothesis were true.
- In other words, the probability of getting such results under the null hypothesis is 5%.

6. What is a hypothesis test? 

The statistical significance of an analysis is evaluated through hypothesis testing. It helps determine whether the results generated were random. The process begins with developing the null hypothesis (H₀) and articulating it. Next, the p-value is computed. Other values cannot be interpreted unless the null hypothesis is assumed.

The alpha level (α) is the set threshold for significance, and changes are made based on it. The p-value should be a value less than alpha; otherwise, the null hypothesis is rejected, and vice versa. A null hypothesis being rejected is a blatant sign of statistical significance.

7. Why are statistical data referred to as "observational" and "experimental"?

 Observational data comes from observational studies. Variables are observed to check for correlations.

Experimental data is statistical data collected from experimental studies. Variables are controlled or manipulated to identify causal relationships and discrepancies.

Moving on to the next set of statistics interview questions and answers.

8. In statistics, what does KPI mean?

 KPI expands as a key performance indicator. It comes under the field of business analytics, as it measures the effectiveness of the company/individual. An excellent example of a KPI is the expense ratio.

9. What is an outlier? How can a dataset's outliers be identified?

 When compared to other observations in the dataset, these data points exhibit significant variation. Depending on the statistical analysis techniques used, outliers may reduce a model's accuracy.

Outliers can significantly affect model performance, especially in statistics for machine learning scenarios.

We’ve covered the basic statistics. Now we’re going to take a quick tour through the intermediate and advanced concepts.

Intermediate statistics interview questions

Under the intermediate statistics interview questions, you will come across practical, slightly complex, and real scenarios.

1. Explain the confidence interval. 

Let's say you have gathered a range of statistical data. The true population parameter is probably within the confidence interval range. 

For example: 

The average results of class 10 range from 60% - 75%, and we can say it with 95% confidence. This means we’re pretty sure (95% sure) that the true average result lies between 60% and 75%.

2. Speak on types of biases. (This is an important statistics interview question.)

Mistakes can occur in sample data while performing statistical analysis. Sampling bias is one such issue, and it can appear in different forms. The main types of sampling bias include:

- Undercoverage Bias
- Observer Bias
- Survivorship Bias
- Self-Selection/Voluntary Response Bias
- Recall Bias
- Exclusion Bias

3. Explain type I vs. type II errors. (Type I vs Type II errors are key concepts in statistical analysis methods for hypothesis testing.)

Type I error (false positive)—occurs when we incorrectly reject the null hypothesis even though it is actually true.

Type II error (false negative)—occurs when we fail to reject the null hypothesis even though it is false 

Type I and II errors are important considerations in business statistics research.

4. What is skewness?

If you come across these statistics interview questions, here's a sample answer:

Skewness measures the asymmetry in data distribution centered around the mean. It is a part of the statistics math fundamentals.

5. What is Bessel’s correction?

There is a high possibility that inaccurate results will arise when sample data is collected. Bessel's correction gives an accurate standard deviation estimate by adjusting the computation.

6. What types of elements are used to calculate Pearson's correlation coefficient?

In most cases, quantitative variables like ratios or intervals are used for Pearson’s correlation coefficient.

You can also check this out for your reference: statistics interview question.

Statistics interview questions for experienced

Statistics interview questions for experienced candidates are a bit more advanced, comprising technical concepts. They often involve real-world applications, which are crucial for professionals working in statistics for data science.

1. How does one identify the p-value in Microsoft Excel?

Follow these instructions to identify the p-value in MS Excel:

- Open the Data tab.
- Select the Data Analysis icon. You will find it in the Analysis tab.
- Choose Descriptive Statistics and click OK.
- Choose the relevant column.
- Enter the confidence level along with other variables.

Hurray, we've almost reached the end of this blog: statistics interview questions. Good job!

2. What is Markov Chain Monte Carlo?

MCMC is a handy tool when picking random samples from a probability distribution becomes complicated. It’s especially useful in Bayesian statistics, where models are often so complex that doing the statistics math directly is nearly impossible. MCMC helps with this by estimating the updated probabilities (posterior).

Statistics in medicine also make use of Markov models.

It allows researchers to study possible paths of disease development and treatment responses.

3. What is causal inference?

Causal inference is about how a change in one variable directly determines or causes a change in another variable. It basically defines a cause-and-effect relationship between two factors.

For example, it can help determine whether a new medicine truly improves recovery. This topic often appears in many statistics courses and is a favorite in statistics interview questions.

Know your facts: Causal inference is often applied in statistics in medicine to determine if treatments truly affect outcomes.

4. With a standard deviation of 100, the average test score equals 500. Sarah’s z-score is 1.5. What is her actual test score?

X= μ+Zσ
where,
μ = mean
σ = standard deviation
Z = z-score.
X=500+(1.5×100)
X=500+150=650

5. Can we say that the median and mean of a perfectly symmetric distribution are always equal? Answer yes or no.

Yes.

6. A regression analysis between advertising spend (x) and sales (y) led to the least-squares line: y = 50 + 5x. What is the implication if advertising spend is increased by 1 unit?

If advertising spend is increased by one unit, there will be an increase of 5 sales since the equation is

y = 50 + 5x.

7. There is a 30% chance of snowfall every day. How likely is it that there will be at least one snowfall in the next five days?

Step 1: The probability that it doesn’t snow in a day
=1−P(Snow)=1−0.3=0.7

Step 2: The probability of no snowfall on all 5 days.
=(0.7)5=0.16807

Step 3: So, the probability of a snowfall at least once in 5 days
=1−P(No snow on all 5 days) =1−0.16807=0.83193

8. Give the mean, median, and mode formulas.

Mean formula:

Median formula:

If the number of data is odd

If the number of the dataset is even

Mode formula: 

Mode is the value that occurs most frequently.

Final Thoughts

Here we have accumulated the most asked statistics interview questions for your reference. Hope this will prove beneficial. Break a leg on your next interview!

Fun Fact: NASA used Statgraphics® to boost the reliability of rocket components in the Space Shuttle and other missions.

Source: NTRS—NASA Technical Reports Server.

FAQs

1. What kind of statistics interview questions are asked to experienced professionals?

They often involve real-world applications, which are crucial for professionals working in statistics for data science. For example: bias-variance tradeoff, Bayesian statistics, Markov Chain Monte Carlo, and causal inference.

2. What is a Poisson distribution?

It is a discrete probability distribution that predicts the number of times an event occurs in a fixed period of time or space. It is effective for independent, rare, and consistently occurring events. Its main characteristic is that it works with counts, i.e., whole numbers, and the resulting average is equal to the variance.

For example, a Poisson distribution can estimate how many emails you receive in an hour.

This concept frequently appears in statistics interview questions. So be thorough with it.

3. How can I get ready for an interview in statistics?

I would recommend visiting blogs with top statistics interview questions. Build a strong foundation in statistical concepts with the help of statistics courses. Daily practice is required to solve real-world problems. You can try learning with Sprintzeal.

4. What is an advanced statistic?

Advanced statistics comprises intricate models and sophisticated methods. Application is hard, specifically in the case of real-world scenarios. But it can be quite useful if it provides results that are figuratively easy to understand.