A Complete Guide to Analyzing Case Interview Graphs & Charts
You are almost guaranteed to be given a few graphs and charts to analyze in your upcoming case interview. Correctly interpreting these exhibits is critical to acing your case.
Some of the information in these exhibits will be useful while other information will not be. You’ll be expected to understand the data in these graphs and charts quickly and identify the key insights that will shape your recommendation.
Given the importance of reading exhibits, how can you ensure that you do well in this part of the case interview?
This article contains everything you need to know. We’ll cover:
- The 6 steps to analyze graphs and charts
- The 10 most common charts and graphs in case interviews
The 6 Steps to Analyze Case Interview Graphs & Charts
There are six steps to reading and interpreting exhibits effectively.
Step 1: Read the chart or graph title
The first step is to get an overall understanding of what the chart or graph is showing. The most efficient way to do this is to read the title of the chart or graph before you look at anything else. This will reveal exactly what information or data is being presented.
Step 2: Look at the axes, units, and labels
Now that you broadly know what information or data is being presented, the next step is to look at the axes. Most charts or graphs will have two axes, the x-axis and the y-axis.
The axes will tell you what dimensions of information are being shown. They should also show the units of measurement, which you should pay particularly close attention to. Remember that numbers are not useful if you don’t know what the units are.
Finally, look at any other labels, such as a legend or key.
The goal of this step is to orient you on how the chart or graph is structured. Once you know how the chart or graph is structured, it will be easier to read.
Step 3: Identify the one or two biggest insights
Next, you want to focus on identifying the one or two biggest insights that immediately stand out. There are a few common patterns you should recognize as you practice interpreting graphs and charts:
- One number may be much smaller or larger in size compared to other numbers
- One number may be increasing or decreasing much more quickly or slowly than other numbers
- The data may show a particular trend, either increasing or decreasing
- There may be a correlation between two different variables
Many candidates make the mistake of reading off every number that the chart or graph shows. Remember that reading text does not get you any points with the interviewer. Interpreting what you read to draw insights is what matters.
Therefore, resist the urge to talk through everything that you see. Start by talking through the one or two most obvious insights that stand out.
Step 4: Identify the less obvious insights
After you identify the one or two biggest insights, take some time to identify other important, but less obvious insights. These are the insights that distinguish outstanding case interview candidates from average candidates.
There are a few common patterns you should recognize when identifying these insights:
- You may need to make some sort of calculation to identify insights
- You may need to compare other information about the case that you already have with the data in the chart or graph
- If the interviewer gives you multiple exhibits to analyze, you may need to compare data across two or more exhibits
Again, resist the urge to talk through everything that you see. Focus your attention on identifying insights before presenting your thoughts.
Step 5: Connect the insights to the case objective
Now that you have identified all of the insights in the chart or graph, you need to answer the question: “so what?” How does this insight help you solve the case or develop a recommendation?
You need to take the insights you have identified and connect it to the case objective. This is what distinguishes outstanding case interview candidates from average candidates.
The insights from the chart or graph should help you develop a hypothesis for what a potential answer to the case could be. If you already had a hypothesis, it should help you refine it. Additionally, the insights should help you identify the potential next steps you need to take to solve the case.
Step 6: Summarize what you have done
Depending on how complex the chart or graph is or how much time you spent analyzing it, you may find it helpful to summarize everything you have done.
You should do this in the following structured way:
- State what the chart or graph shows
- List the biggest insights drawn from the chart or graph
- Explain how these insights impact your hypothesis or answer to the case
- Propose next steps to take to solve the case
If you consistently follow this six step approach to reading and interpreting charts and graphs, you will find yourself getting much quicker and better at analyzing exhibits.
The 10 Most Common Charts & Graphs in Case Interviews
1. Simple Bar Chart
One of the simplest charts is the bar chart. In this example, the x-axis represents different products, which includes desktops, laptops, and tablets. The y-axis represents sales in dollars. Therefore, the height of each of these bars represents the amount of sales for each product.
Simple bar charts are straightforward to read and interpret since they don’t show that much information. In this example, we can conclude that laptops have the highest sales at $5,000 and tablets have the lowest sales at $1,500.
2. Stacked Bar Chart
A stacked bar chart adds another dimension of data to a simple bar chart.
In this example, the x-axis represents different companies. The y-axis represents sales in dollars. The stacked segments in each of the bars represents the type of product. Therefore, this stacked bar chart shows the sales of different products by company.
We can conclude that Company B has not only the highest sales, but also the highest sales in each of the three product categories.
3. 100% Stacked Bar Chart
A 100% stacked bar chart transforms the y-axis of a stacked bar chart.
In this example, instead of the y-axis being sales in dollars, the y-axis is now sales as a percentage of total sales for that company. The x-axis still represents the company and the stacked segments still represent products.
The advantage of a 100% stacked bar is that you can easily compare the relative proportion of a segment in one bar with that same segment in another bar.
In this example, we can conclude that out of all three companies, Company B has the highest proportion of sales coming from desktops. We can also conclude that Company C has the highest proportion of sales coming from tablets.
4. Marimekko / Mekko Chart
The next chart is called the Marimekko or Mekko chart, which adds yet another dimension of data to the 100% stacked bar chart. This chart is heavily used by Bain & Company and may be confusing to those who have never seen it before.
In this example, the x-axis represents the different companies, the y-axis represents the percentage of total sales, and the stacked segments represent the different products. The additional dimension of data is the width of the x-axis, which shows how large total sales are across the different companies.
You can think of Marimekko or Mekko charts as a large, rectangular pie chart. In this example, the entire area of the full rectangle represents $24,500 of sales, the sum of total sales across all three companies. Each individual rectangle represents the percentage of the total $24,500 in sales.
Just like for 100% stacked bar charts, you can easily compare the relative proportion of a segment in one bar with another in a Mekko chart. In this example, you can see that the proportion of sales from tablets is highest in Company C since its tablet segment is the tallest.
However, in a Mekko, you can also compare the size of one entire bar with another. In this example, you can see that Company B has the highest overall sales since the width of its bar is the widest.
5. Pie Chart
The next chart is the pie chart, which is heavily used by the Boston Consulting Group (BCG). A pie chart shows the same information as a 100% stacked bar chart.
In this example, the pie chart represents 100% of sales by product line. Each slice of the pie represents the proportion of total sales each product category accounts for.
6. Waterfall Chart
A waterfall chart shows or reconciles how we get from one number to another number.
In this example, the chart shows how we get from year one profit, represented by the first bar furthest to the left, to year two profit, represented by the last bar furthest to the right. Upon initial inspection, we see that profit has increased from year 1 to year 2. What caused the increase?
The bars in light blue show drivers that increased profits. Price increase, quantity increase, and a decrease in variable costs all caused profits to increase.
The bar in dark blue shows what driver decreased profits. An increase in fixed costs decreased profits.
Collectively, all of these drivers resulted in a net increase in profits. We can conclude that the largest driver behind the increase in profit is the quantity increase because that is the largest bar.
A histogram may look like a simple bar chart, but it is quite different. A histogram shows the distribution of a variable. A bar chart, on the other hand, compares a variable.
In this example, the x-axis represents different age groups. The y-axis shows the frequency of these age groups. From this histogram, we can conclude that the 81+ years age group has the fewest number of people. The 21 - 40 years age group has the greatest number of people.
8. Line Graph
A line graph shows a change in a variable over time. Time is almost always on the x-axis for line graphs.
In this example, the x-axis shows years and the y-axis shows annual revenue. This graph shows how annual revenue has changed over five years.
A scatterplot shows points to visualize the values of two different variables. These two variables are labeled on the x-axis and y-axis.
In this example, the x-axis represents annual growth in supply chain investments and the y-axis shows annual revenue growth.
If we look for patterns among the points, it appears that as annual growth in supply chain investments increases, annual revenue growth increases. A trendline is used in scatterplots to show this correlation.
We can use trendlines to make predictions. For example, we could conclude that if a company’s annual growth in supply chain investments is 10%, then its annual revenue growth would be greater than 20%.
10. Bubble Chart
Bubble charts show many dimensions of information. Bubble charts use the x-axis, y-axis, size of the bubble, and color of the bubble to show data.
In this example, each bubble represents a different drug. The x-axis shows drug efficacy, the y-axis shows mortality rate, the size of the bubble shows sales in dollars, and the color indicates which company the drug belongs to.
With bubble charts, you typically want to identify which quadrant of the chart is the best or most favorable quadrant. In this example, drugs with high efficacy rates and low mortality rates are the best.
So, looking at the quadrant in the bottom right, we see that drugs in this segment have the highest sales, which makes sense intuitively. Additionally, we see that Company A has two drugs in this quadrant while Company B only has one.
However, Company B has the drug with the highest amount of sales. This is likely due to the fact that the drug has a very low mortality rate but a high efficacy rate.
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