The MMI data interpretation and calculation station isn’t many people’s idea of fun. Hard to think why- who doesn’t love mental maths under time pressure!

Don’t worry, I’m going to explain some key concepts that will make this station a lot less daunting and a lot more manageable. Here’s a quick summary:

**Data interpretation in an MMI usually revolves around a ‘describe’ or ‘explain’ question regarding a graph/table/chart****If it’s ‘describe’ you just need to say what you see! If it’s ‘explain’ then you’ll have to apply your scientific knowledge****Being hot on your mental maths is always going to help in calculation questions. Get practising before your interview!****Two interviewer favourites are converting between units and strengths of solutions. Make sure you’re confident in both areas**

With a bit of practice, you’ll soon be a certified MMI maths whizz- which will come in handy as you can almost guarantee you’re going to have some element of calculation or data interpretation as part of your interview.

At the end of the guide, I’ve even prepared three practice questions for you to test your mettle.

## How To Approach The MMI Data Interpretation & Calculation station

You’ll be pleased to know you don’t have to be the next Steven Hawking to pass the MMI data interpretation & calculation station.

**At the end of the day, you’re interviewing for medicine, not maths.**

What the medical schools are trying to establish is if you’ve got a good basic grasp of converting units, interpreting data and simple calculations.

These skills are highly relevant to the work of a junior doctor.

For example, you’ll often have to calculate drug doses on the ward or review scientific papers.

Medical schools vary in how they test these skills:

- Some focus heavily on the data interpretation
- Others more so on the calculation questions
- These may be tested in the same or separate stations

I’m going to look at data interpretation and calculation questions individually in this guide, but my practice questions at the end combine the two domains.

## How To Master MMI Data Interpretation

Medical schools love to put applicants face-to-face with a new graph or table and ask them to interpret it.

A pretty intimidating task considering the data is often pulled from some complex scientific research.

There are generally two common lines of questioning regarding the data:

- Being asked to
**describe**the graph/table/chart - Being asked to
**explain**or*draw conclusions*from the graph/table/chart

Let’s look at them each in turn…

### Describing The Data

Candidates often throw away marks when asked to describe data because they don’t state the obvious!

Understandably, they’re trying to show-off their scientific acumen but in doing so often stray far into explaining the data rather than describing it.

**The golden rule of describing data in an MMI is to say what you see.**

Here’s my foolproof method for describing data in an MMI:

- Describe the
*way*the data has been presented. Is it a*graph/table/chart?* - State the
**title**of the graph/table/chart - State the
**axes**of the graph*(or headings of a table)*and their**units** - Describe the
**overall trend**you can see - Focus in on any other
**minor trends** - Use
**values**from the axes to illustrate your statements

Let’s now look at how this would relate to an example:

**Please describe this graph.**

*“This is a graph showing the effects of gonadotropin-releasing hormone analogs on the overall survival of premenopausal women with breast cancer.”“On the x-axis the length of follow-up is plotted from 0-36 months. On the y-axis the overall survival is plotted in percentage.““There are two lines plotted on this graph. One for the treatment group and one for a control group. They start at 100% survival at 0 months and both trend down as the length of follow-up increases.”“Importantly, the treatment group trends downwards at a slower rate than the control group. For example, at 36 months the control group has a survival of roughly 60% whereas the treatment group’s survival is approximately 75%.”*

*“The control group’s survival initially*

**sharply**decreases from 0-18 months before relatively plateauing at 18-36 months. This is in contrast to the treatment group that maintains a more**steady**decrease in overall survival across the length of the follow-up period.”### Drawing Conclusions From The Data

Questions that ask you to explain or draw conclusions from the data require your higher-level scientific reasoning.

This is where you need to think about what the data is actually telling us and what mechanisms might be behind the trends we’re seeing.

You may have to draw on A-level biology or chemistry knowledge so make sure you’ve brushed up a bit before your interview.

**Please explain what conclusions you can draw from this graph.**

*“This graph shows that at 36 months the treatment group have an increased overall survival compared to the control group.”*

*“This would suggest that gonadotropin-releasing hormone analogs*

**increase survival**in women with breast cancer.”*“The treatment group*

**avoid**the initial sharp decrease in survival of the control group between 0-18 months.”*“This might suggest the overall survival benefit is afforded as a result of the gonadotropin-releasing hormone analog’s effects in the*

**first 18 months**of treatment.”*“Certainly, in the last 12 months of the trial the two group’s survival seems to*

**mirror**each other quite closely- although this may be an arbitrary correlation due to the restricted follow-up period.”## How To Excel In MMI Calculation Questions

For MMI calculation questions it’s always going to be an advantage if you’ve done a bit of mental maths practice.

I remember in the run up to my MMI I got my brother to fire simple multiplication or division questions at me for fifteen minutes a day.

*(Hint: bribes with chocolate were required…)*

Now it doesn’t have to be a family member, maybe a friend or even just find a resource like this one.

All you need is a list of simple calculations you can run through and test yourself with.

Now two areas that medical schools particularly love to test are strength of solutions and converting between units.

### Converting Between Units

There’s nothing worse than putting an answer down to a question only to later realise you were out by a factor of ten!

That’s why it’s key you have a really solid grasp of your conversions between basic units of weight and volume.

That’s right, nothing fancy, but you’ll thank yourself later if you can convert these units with 100% confidence.

WEIGHT | 1 gram equals… | 1000 milligrams equals… | 1,000,000 micrograms |

VOLUME | 1 litre equals… | 100 centilitres equals… | 1000 millilitres |

Get comfortable with quickly converting different values into the same units. This will make any calculations you do a thousand times easier.

For example:

- 750
**μg**= 0.75**mg** - 25
**cl**= 250**ml** - 7700
**mg**= 7.7**g**

*“You are asked to give a patient a 10mg intramuscular injection of the drug haloperidol. The syringe contains 0.05g in 1cl. What volume in millilitres of the solution do you need to give?” *

*So we know the syringe contains 0.05g/1cl.*

*Converting the centilitres to millilitres gives us 0.05g/10ml.*

*So in 1ml we’d have 0.005g of haloperidol.*

*0.005g x 1000 = a 5mg per 1ml solution.*

*We want to give the patient 10mg, therefore we need:*

*10 ÷ 5 =*

*2ml of the solution in the syringe.*### Strength of Solutions

I personally find figuring out strengths of solutions confusing at the best of times.

That’s why for the time-pressured environment of the MMI, I suggest you just learn the formula below:

So that means for a **1%** lidocaine solution there’s **10** *milligrams* of lidocaine per **1 ***millilitre* of the solution.

Or put another way, for a **1%** solution there’s **1** **gram** of solute per **100ml** of solution.

Whichever way seems to make the most sense to you, I’d suggest learning.

You can then use your formula to figure out any of the values needed in individual questions.

*“You are asked to give a patient 20ml of a 10% calcium gluconate solution. How many grams of the drug have you administered?”*

*From our formula we know a 1% solution contains 10 milligrams of solute per 1ml of solution.*

Therefore, a 10% solution contains 100milligrams per 1ml.

Therefore, a 10% solution contains 100milligrams per 1ml.

*If we’re administering 20ml of the solution we’re giving:*

20 x 100milligrams = 2000milligrams =

20 x 100milligrams = 2000milligrams =

**2 grams of calcium gluconate**.*Prepping for a medicine interview?* You might also want to check out my guide on ‘The MMI Communication Station’.

## MMI Data Interpretation & Calculation Practice Questions

The maths tested in the MMI data interpretation & calculation station is usually in the form of a clinical or biological example.

There aren’t going to be any long calculations or difficult formulas (phew).

However, the pressure of the day can mean you might find yourself thinking twice about even simple calculations.

I’ve put together three practice questions to put your theory into action. The answers are just below each one (no peeking).

*Question 1*

This pie chart shows the **proportion** of each age-group that makes up the town ‘*Lemon Meringue*‘.

**A**represents the proportion of the population aged**0-20****B**is all those aged**21-40****C**is all those aged**41-60****D**is all those aged**61 and over**

The town is planning to give the flu vaccine to **all** of their ‘*61 and over*‘ population.

In order to do this, they need to hire **one** person aged *21-40* for every **10** people aged *’61 and over’*.

**a)** If the *’61 and over’* population numbers **6700**, how many people aged *21-40* does the town need to hire?

**b)** Last year, the town vaccinated **6500** people aged *61 and over*. Of those vaccinated, **65** still caught the flu. What *percentage* is this?

**c) **The **death rate** for the flu in those aged *21-40* is **0.01%**. How many *21-40 year-olds* would need to have the flu for **one** to die?

*Question 1 Answers*

*a)* **670**. One person aged 21-40 is needed for every ten aged 61 and over. 6700÷10=670

*b)* **1%**. 65 out of 6500 vaccinated people caught the flu. 65÷6500=0.01 which is 1%

*c)* **10,000**. The death rate is 0.01% and the question asks about one death. 1÷0.0001=10,000

*Question 2*

The pyramid diagram above represents a recent screening program run to detect people with *‘application fever’*.

If a person tested **positive** at the initial screening they were invited back to undergo further testing to *confirm* the diagnosis.

**E**is the size of the population*(880)***D**is the number of people who turned up to the screening event*(560)***C**is the number who tested**positive**from the initial screening*(340)***B**are those who returned to undergo further testing*(220)***A**is the number of people who’s results came back**positive**from the further testing. They were**diagnosed**with*application fever (160)*

**a)** If the 160 people *confirmed* to have application fever go on to infect 320 people, what is the **R value** of the fever?

**b)** What **proportion** of the total population returned for *further* testing?

**c)** These proportions are known to hold true for *any* size population. How many people would be **diagnosed** with *application fever* if the population size was 2640?

*Question 2 Answers*

*a)* **2**. The R value is the average number of people a case goes on to infect.

*b)* **1/4**. 220 returned for further testing out of a population of 880. 220÷880=1/4

*c)* **480**. 2640 is 3 times the size of the current population. Therefore the number of diagnosed cases would be 3 times bigger too. 160×3=480

*Question 3*

The graph above represents the metabolism of the drug ‘*methyl-mono-isorbide*‘ or ‘**MMI**‘ for short.

Blood concentration of ‘**MMI**‘ is recorded on the *y-axis* and time along the *x-axis*. The drug is ingested at **time 0** and the blood concentrations noted until they become *unrecordable*.

The metabolism of *‘MMI’* is known to **increase proportionally** to a patient’s weight. The above graph was created using data from a *60kg* male.

If the patient was *90kg*, answer **true or false** to the following statements:

**a)** At time ‘**x**‘ on the *x-axis*, the blood concentration would be *lower*

**b)** **Point** **C** (the time the drug level becomes **unrecordable**) would be reached in a *quicker* time

**c) **Statement **b)** would hold true *no matter* the dose ingested

*Question 3 Answers*

*a)* **True**. 90kg is heavier than the original test subject (60kg). Therefore the 90kg patient will metabolise the drug quicker and have lower levels at a comparable time.

*b)* **True**. A quicker metabolism will also clear the drug from a patient’s blood faster.

*c)* **False**. Just because their metabolism is faster doesn’t mean they could clear TEN times the dose faster for example.

Final Thoughts

I know the data interpretation & calculation station isn’t everybody’s cup of tea but once you’ve got some of these key techniques down they can be easy marks.

**As with all these things, practice makes perfect.**

I’d recommend a little and often approach to these questions in the run-up to your MMI.

As long as you keep on top of your mental maths and have a go at interpreting some charts from your science textbooks you’ll be sure to smash it come interview day.