Solving Statistics: Should I use Pearson’s or Spearman’s correlation coefficient
Background
A correlation coefficient is a number that shows if there is an association between variables. It provides an indication of the association between two variables X and Y (1). Two types of correlations are commonly used for continuous, numerical data. These are Pearson’s correlation coefficient and Spearman’s rank correlation coefficient.
Clinical Image: An abnormal ovary
Presentation
A 31 year-old woman consulted the gynecologic outpatient clinic complaining of dysmenorrhea, dyspareunia and daily abdominal discomfort since several months. The pain is progressive since ceasing the oral contraceptive pill in order to conceive. She has a regular cycle, with an average duration of 28 days and a menstruation lasting 3-4 days.
Radiology Image: A 65-year-old female
Patient data
- Age: 65 years
- Gender: Female
- Medical history: Hypertension, hypothyroidism
- Initial presentation: Fever for four weeks. Dyspnoea, increasing when laying down. Chest pain.
- Echocardiography: Right ventricle dilatation.
Interview: prof. dr. S. Middeldorp
At the age of 14, I already knew I wanted to study medicine and since then I luckily never doubted that choice. I studied medicine here in Amsterdam at the AMC. It was during clinical lectures that I found out about my interest in internal medicine and my enthusiasm for this specialty was confirmed during my clinical rotations. My dream was to become a really good internist and work in a large, peripheral hospital, like the OLVG.
Subject 101: Polycystic ovarium syndrome (PCOS)
Trial and Error: The Tortoise
To slow! After a quick look at all the feedback forms I gathered during my rounds, I realized that my main reoccurring error was that I was not quick enough. Somehow all my supervisors came to the same conclusion; this young doctor is not able to sprint.
I vividly remember my first feedback form, the pro’s were read and promptly forgotten, but the con’s: oy…they stuck in my mind, making my next round a complete joke. Have you ever seen a tortoise trying to sprint? In my effort to be quick, I lost the joy of learning. I had set aside my holistic ideals in an attempt to improve my weakness. In doing so, I tried to change the nature of my character and guess what: I failed! Not only did I fail, the whole process of trying gave me the feeling that I was not competent, not capable and foremost not good enough to ever succeed in any medical profession. Observing all the hares jumping from one patient to another in an endless winning streak, I lost confidence in myself. However, through trial and error I now know that the goal of negative feedback is not always change. It is the awareness of your speed, your style and your character that is far more important than change itself. Once I realized that, I was not doubtful about my speed anymore, I knew it was part of the way I do best. My advice is to stay true to your character, use feedback to understand your talents and shortcomings, and by doing so become quicker than the hares.