DA0-002 Data Analysis Practice Test 12 — 15 Questions

Question 1

A time series of monthly sales data exhibits a clear upward trend over several years, with consistent peaks each December. Which components are present in this series?

Accepted Answer

Trend and seasonality. The upward trend is a trend component, and the consistent December peaks indicate seasonality.

Answer

Cyclical and irregular components only

Answer

Seasonality and cyclical components only

Answer

Trend and irregular components only

Question 2

In an A/B test, the null hypothesis states that there is no difference between the control and treatment groups. After running the test, the p-value is 0.04. Assuming α = 0.05, what is the correct conclusion?

Accepted Answer

Reject the null hypothesis. Since p-value (0.04) < α (0.05), we reject the null hypothesis, indicating a statistically significant difference.

Answer

Fail to reject the null hypothesis

Answer

Accept the null hypothesis

Answer

The test is invalid because the p-value is too low

Question 3

A data analyst notices that a dataset of customer ages has several missing values. Which method for handling missing data is most appropriate if the data is missing completely at random and the analyst wants to preserve sample size?

Accepted Answer

Impute with the mean age. Mean imputation replaces missing values with the mean, preserving sample size, but can bias estimates. However, for MCAR, it is a common simple approach.

Answer

Forward-fill using the previous value

Answer

Replace missing values with zero

Answer

Delete all rows with missing data

Question 4

A data analyst is cleaning a dataset and finds that some records have duplicate entries based on customer ID. Which data quality dimension is most directly affected by these duplicates?

Accepted Answer

Uniqueness. Duplicates violate the uniqueness dimension, which requires each entity to be represented only once.

Answer

Timeliness

Answer

Consistency

Answer

Accuracy

Question 5

Which statistical test should be used to determine if there is a significant association between two categorical variables, such as gender and product preference?

Accepted Answer

Chi-square test. The chi-square test of independence is used to test association between two categorical variables.

Answer

ANOVA

Answer

Pearson correlation

Answer

t-test

Question 6

An analyst wants to compare the mean sales revenue across three different store regions. The data is normally distributed and variances are equal. Which statistical test is most appropriate?

Accepted Answer

ANOVA. ANOVA (Analysis of Variance) is used to compare means of three or more groups.

Answer

Two-sample t-test

Answer

Paired t-test

Answer

Chi-square test

Question 7

A data team is preparing data for a clustering analysis. Which THREE of the following steps are commonly part of data cleaning?

Accepted Answer

Removing duplicate records. Data cleaning includes handling missing values, outlier treatment, and deduplication.

Answer

Calculating the mean

Answer

Training a regression model

Question 8

An analyst is conducting an A/B test on a new website layout. Which TWO of the following must be defined before the test begins?

Accepted Answer

The significance threshold (alpha). Sample size and significance level must be set a priori to ensure proper test design.

Answer

The final conversion rates for each group

Answer

The actual p-value from the test

Answer

The confidence interval for the lift

Question 9

Which TWO of the following are true about Pearson correlation coefficient (r)?

Accepted Answer

It measures the strength and direction of a linear relationship. Pearson r ranges from -1 to 1, measuring linear relationship; +1 indicates perfect positive linear correlation.

Answer

An r of 0 means no relationship exists

Answer

It ranges from 0 to 1

Answer

It can be used for categorical variables

Question 10

A data analyst calculates the mean, median, and mode of a sales dataset and finds they are all equal. Which type of distribution does this indicate?

Accepted Answer

Normal distribution. When mean, median, and mode are equal, the distribution is symmetric and typically bell-shaped (normal).

Answer

Skewed right

Answer

Bimodal distribution

Answer

Skewed left

Question 11

A retailer wants to test if a new website layout increases the average time spent on the site. They split traffic: control group (old layout) and treatment group (new layout). Which statistical test is most appropriate to compare the average time spent between the two groups?

Accepted Answer

Two-sample t-test. A t-test is used to compare means of two independent groups.

Answer

ANOVA

Answer

Pearson correlation

Answer

Chi-square test

Question 12

A data scientist builds a logistic regression model to predict customer churn (yes/no). The model outputs a probability of 0.75 for a particular customer. Which of the following best describes this output?

Accepted Answer

There is a 75% chance the customer will churn.. Logistic regression outputs a probability between 0 and 1, interpreted as the likelihood of the positive class (churn = yes).

Answer

The customer will definitely churn.

Answer

The odds of churning are 0.75 to 1.

Answer

The model is 75% accurate.

Question 13

A dataset contains employee salaries ranging from $30,000 to $200,000. An analyst wants to scale the salaries to a range of 0 to 1 for use in a distance-based clustering algorithm. Which method should they use?

Accepted Answer

Min-max normalization. Min-max normalization scales data to a 0-1 range.

Answer

Log transformation

Answer

Robust scaling

Answer

Z-score standardization

Question 14

A marketing team runs an A/B test on email subject lines. The p-value is 0.03 with α = 0.05. Which of the following is the correct interpretation?

Accepted Answer

Reject the null hypothesis; there is a statistically significant difference.. Since p-value (0.03) < α (0.05), we reject the null hypothesis, indicating a statistically significant difference.

Answer

The result is not statistically significant at the 95% confidence level.

Answer

The probability that the null hypothesis is true is 3%.

Answer

Fail to reject the null hypothesis; no significant difference.

Question 15

An analyst uses K-means clustering on customer purchase data. After plotting the within-cluster sum of squares for different values of k, they observe an elbow at k=4. What is the most appropriate number of clusters?

Accepted Answer

4. The elbow method suggests choosing k where the WSS starts to diminish slowly; that point is the elbow.

Answer

6

Answer

5

Answer

3