# Web Tortoise

## 2012-May-03

### Half Full or Half Empty? Choosing a Statistical Calculation

Response:

Hello! This was written 2012-MAY-03 at 12:27 PM ET.

Question: In your life as a Keynote or Catchpoint user, suppose you have a day’s worth of website response time performance data. Should you average using the Arithmetic Mean or the Geometric Mean?

Answer: Assume you want to use a central-tendency calculation like a mean (we’ll talk about percentiles in another post). Since the Geometric Mean will result in a lower value than the Arithmetic Mean, you might say the Geometric Mean is an “optimistic calculation” where the Arithmetic Mean is a “pessimistic calculation”. See the below going from raw data to line chart, then decide for yourself when to use either of the two calculations.

First, the below scatter plot shows a day’s worth of website response time data. In this case, there are about 2,880 total data, or about 120 per each respective 24 hours in a day. Notice the single spurious outlier in the 03:00 AM hour.

Second, the above scatter plot is then transformed into the below line graph. The blue line calculates the data using the Arithmetic Mean and the red line calculates the same set of data using the Geometric Mean. The single spurious outlier in the 03:00 AM hour caused a “spike” to appear in the line graph.

Fair warning, the perceived impact (a.k.a. “The Spike”) will depend on how many data are being averaged. The point remains the same, though: The Arithmetic Mean is more subject to skew from spurious outliers than the Geometric Mean. So, depending on your situation, you may want to choose one or the other (or both to see the delta, which is another powerful way to analyze).

_The following is optional reading material._

For a refresher on calculating the geometric mean in excel, see this post http://webtortoise.com/2012/03/16/geometric-mean-in-excel/

#Keynote ; #Catchpoint ; #Gomez ; #KeynoteUser ; #Catchpointuser ; #Gomezuser ; #ArithmeticMeanvsGeometricMean ; #ExcelStatistics

## 2012-Mar-07

### Christmas in Excel

Response:

Hello! This was written 2012-MAR-07 at 01:42 PM ET.

Use color to add value to your Performance charts. Red and green columns overlay your line chart where red equals an “increase in Response time from previous interval” and green equals “decrease in Response time from previous interval”.

The following excel waterfall chart has the aforementioned conditions applied (red equals an “increase in Response time from previous interval” and green equals “decrease in Response time from previous interval”). In this case, the waterfall chart is showing week-over-week Response time for a landing page. Credit to peltiertech.com for the waterfall template; my additional formatting has been applied.

_The following is optional reading material._

Suppose you’re an academic site, perhaps a Search Engine or a Reference site. You might theorize the September change in Response time is impact from everyone going ‘back to school’. To further your theory, notice the December change, when everyone is ‘home for the holidays’. What else might you look for? Maybe three ‘reds in a row’, to spot a trend?

Search for the PeltierTech article:  http://www.ask.com/web?q=excel+waterfall+chart+peltiertech

# Excel conditional formatting ; Excel conditional charting ; Web Performance Optimization ; Catchpoint ; Keynote ; Gomez ; Excel ; Statistics

## 2012-Feb-29

### Introduction

Filed under: Introduction — Tags: , , , , , , — leovasiliou @ 11:10 AM EDT

Response:

Hello! This was written 2012-FEB-29 at 10:54 AM ET.

Welcome to The Web Tortoise and Hare‘s inaugural post. If you are a Catchpoint, Keynote, Gomez or etc user, then this is for you!

Here will be discussed various web availability, performance and “plus plus” topics. Will slant toward using excel to get additional value from the data provided by companies like Catchpoint, Keynote and Gomez.

Availability: Did you get a response from the server?

Performance: After the response, how long did it take for your web page to load?

“Plus Plus”: Could the time of day have affected the web page load? What other factors might influence either availability or performance? Geography? Ad Serving? Else?