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How Could You Benefit from Plackett & Burman Experimental Designs ?

Screening experimental designs allow you to study a very large number of factors in a very limited number of runs. The objective is to focus on the few factors that have a real effect and eliminate the effects that are not significant. This is often the initial typical objective of any experimenter when a DOE (design of experiments) is performed.

Table of Factorial Designs

Consider the table below. In Minitab, you can quickly access this table of factorial designs by selecting Stat > DOE > Factorial > Create Factorial Design... and clicking "Display Available Designs." The table tells us the...

Using the G-Chart Control Chart for Rare Events to Predict Borewell Accidents

by Lion "Ari" Ondiappan Arivazhagan, guest blogger

In India, we've seen this story far too many times in recent years:

Timmanna Hatti, a six-year old boy, was trapped in a 160-feet borewell for more than 5 days in Sulikeri village of Bagalkot district in Karnataka after falling into the well. Perhaps the most heartbreaking aspect of the situation was the decision of the Bagalkot district administration to stop the rescue operation because the digging work, if continued further, might lead to collapse of the vertical wall created by the side of the borewell within which Timmanna had struggled for...

Angst Over ANOVA Assumptions? Ask the Assistant.

Do you suffer from PAAA (Post-Analysis Assumption Angst)? You’re not alone.

Checking the required assumptions for a statistical  analysis is critical. But if you don’t have a Ph.D. in statistics, it can feel more complicated and confusing than the primary analysis itself.

How does the cuckoo egg data, a common sample data set often used to teach analysis of variance, satisfy the following formal assumptions for a classical one-way ANOVA (F-test)?

  • Normality
  • Homoscedasticity
  • Independence

Are My Data (Kinda Sorta) Normal?

To check the normality of each group of data, a common strategy is to display...

How Could You Benefit from Between / Within Control Charts?

Choosing the right type of subgroup in a control chart is crucial. In a rational subgroup, the variability within a subgroup should encompass common causes, random, short-term variability and represent “normal,” “typical,” natural process variations, whereas differences between subgroups are useful to detect drifts in variability over time (due to “special” or “assignable” causes). Variation within subgroup is therefore used to estimate the natural process standard deviation and to calculate the 3-sigma control chart limits.

In some cases, however, identifying the correct rational subgroup is...

A Fun ANOVA: Does Milk Affect the Fluffiness of Pancakes?

by Iván Alfonso, guest blogger

I'm a huge fan of hot cakes—they are my favorite dessert ever. I’ve been cooking them for over 15 years, and over that time I’ve noticed many variation in textures, flavor, and thickness. Personally, I like fluffy pancakes.

There are many brands of hotcake mix on the market, all with very similar formulations. So I decided to investigate which ingredients and inputs may influence the fluffiness of my pancakes.

Potential factors could include the type of mix used, the type of milk used, the use of margarine or butter (of many brands), the amount of mixing time, the...

How Accurate are Fantasy Football Rankings?

The calendar just flipped to August, meaning it’s time to get ready for fantasy football season! As you prepare for your draft, you will no doubt be looking at all sorts of rankings. But when the season is over, do you ever go back and see how accurate those rankings were? And are rankings for some positions more accurate than others? Well that’s exactly what we’re going to find out!

I went back the previous 5 seasons and found ESPN’s preseason rankings for quarterbacks, running backs, wide receivers, and tight ends. I know that different publications will have slightly different rankings, but...

Blind Wine Part IV: The Participants

In Part I, Part II, and Part III we shared our experiment, the survey results, and the experimental results. To wrap things up, we're going to see if the survey results tied to the experimental results in any meaningful way...

First, we look at whether self-identified knowledge correlated to the total number of correct appraisals:

We have no evidence of a relationship (p = 0.795).  So we'll look at the number correct by how much each participant usually spends:

Again, no evidence of a relationship (p = 0.559).  

How about how many types each regularly buys?

There appears to be something here,...

Blind Wine Part I: The Experiment

Already relaxed on his first day in Napa, Brutus and his wife Suzy decide to visit their favorite winery just before lunch to taste their new Cabernet Sauvignon. The owner recognizes them as they walk in the door and immediately seats them on the patio overlooking the vineyard. Two glasses appear, and as the owner tells them about the new Cabernet, Brutus prepares for an onslaught of blackberry and plum flavors, with some notes of vanilla and leather.

The wine is poured and as Brutus swirls it in his glass and breathes in the aromas, he picks up some of the oak infused into the wine as it aged...

Where Did All the World Cup Goals Go? Find Out with a 2-Sample Poisson Rate Test

A few weeks ago I looked at the number of goals that were being scored in the World Cup. At the time there were 2.9 goals per game, which was the highest since 1970. Unfortunately for spectators who enjoyed the higher scoring goals, this did not last.

By the end, the average had fallen to 2.7 goals per game, the same amount scored in the 1998 World Cup. After such a high-scoring start, the goals per game fell off and ended up being pretty similar to other recent World Cups.

What happened?

Comparing the Group Stage to the Knockout Stage

After 15 straight days of games in the group stage, there...

Two-Way ANOVA in Minitab 17

After upgrading to the latest and greatest version of our statistical software, Minitab 17, some users have contacted tech support to ask "Wait a minute, where is that Two-Way ANOVA option in Minitab 17?" 

The answer is that it’s not there. That’s right! The 2-Way ANOVA option that was available in Minitab 16 and prior versions was removed from Minitab 17. Why would this feature be removed from the new version?  Shouldn’t the new version have more features instead of less? 

Two-Way ANOVA was removed from Minitab 17 because you can get the same output by using the General Linear Model option in...

Guest Post: Did Ma's Diabetes Get Cured by Back Surgery?

The Minitab Fan section of the Minitab blog is your chance to share with our readers! We always love to hear how you are using Minitab products for quality improvement projects, Lean Six Sigma initiatives, research and data analysis, and more. If our software has helped you, please share your Minitab story, too!

Once my Mom was diagnosed with Diabetes Type II, I began to track her blood sugar readings in Minitab Statistical Software.

I did it three times a day before meals...over weeks, then months, then years. At each doctor's appointment I would take in her 'book' of readings, and I would...

Bar Chart: Where to Start?

Whether you’re just learning statistics or you're already using data analysis on the job, there are not many tools more straightforward than a bar chart. Bar charts are effective at getting across their message, and are used in a diverse number of fields, from service quality to pharmaceuticals to manufacturing.

However, I’ve noticed recently that a lot of customers looking to create a bar chart are surprised at how many different options are presented when you go to Graph > Bar Chart... in Minitab. There are, in fact, 14 different options based on 1) what you want your final graph to...

Can I Just Delete Some Values to Reduce the Standard Variation in My ANOVA?

We received the following question via social media recently:

I am using Minitab 17 for ANOVA. I calculated the mean and standard deviation for these 15 values, but the standard deviation is very high. If I delete some values, I can reduce the standard deviation. Is there an option in Minitab that will automatically indicate values that are out of range and delete them so that the standard deviation is low?

In other words, this person wanted a way to automatically eliminate certain values to lower the standard deviation.

Fortunately, Minitab 17 does not have the functionality that this person was...

Using Probability Plots to Understand Laser Games Scores

There is more than just the p value in a probability plot—the overall graphical pattern also provides a great deal of useful information. Probability plots are a powerful tool to better understand your data.

In this post, I intend to present the main principles of probability plots and focus on their visual interpretation using some real data.

In probability plots, the data density distribution is transformed into a linear plot. To do this, the cumulative density function (the so-called CDF, cumulating all probabilities below a given threshold) is used (see the graph below). For a normal...

The 6 coolest tools on Minitab's toolbars

Toolbars are there to make your life easier, but if you don’t take the time to hover over each button and wait for a description, it’s pretty easy to never know that there’s a faster way to do something.

The toolbars in Minitab Statistical Software include some pretty nifty shortcuts. Here are my favorite 6:

StatGuide

As soon as you have results in Minitab, the StatGuide button becomes active on your toolbar. Click the button, and the StatGuide opens directly to guidance for the analysis that you’re looking at. Minitab saves you the time you would have spent looking for information about your...

The Five Coolest Things You Can Do When You Right-click a Graph in Minitab Statistical Software

Minitab graphs are powerful tools for investigating your process further and removing any doubt about the steps you should take to improve it. With that in mind, you’ll want to know every feature about Minitab graphs that can help you share and communicate your results effectively. While many ways to modify your graph are on the Editor menu, some of the best features become available when you right-click your graph.

Here are the five coolest things you can do when you right-click a graph in Minitab Statistical Software.

Send graph to...

Once your graph is ready for your report or presentation,...

An Unlikely Statistician: Florence Nightingale

Many of my close friends and family members are nurses, and I’ve noticed (via Facebook of course) that many recently celebrated National Nurses’ Week, which ran Tuesday, May 6 through Monday, May 12—the actual birthday of Florence Nightingale.

Florence Nightingale is known as the founder of modern nursing, but you might not know that she is also a celebrated statistician. When I started reading more about her contributions to statistics, I was surprised to find that she used statistics to not only learn more about how many people died during wartime, and why, but also as a way to visually...

Gage This or Gage That? How the Number of Distinct Categories Relates to the %Study Variation

We cannot improve what we cannot measure. Therefore, it is critical that we conduct a measurement systems analysis (MSA) before we start analyzing our data to make any kind of decisions.

When conducting an MSA for continuous measurements, we typically using a Gage R&R Study. And in these Gage R&R Studies, we look at output such as the percentage study variation (%Study Var, or %SV) and the Number of Distinct Categories (ndc) to assess whether our measurement system is adequate.

Looking at these 2 values to assess a measurement system often leads to questions like "Should I look at both values? ...

Dividing a Data Set into Training and Validation Samples

Adam Ozimek had an interesting post April 15th on the Modeled Behavior blog at Forbes.com. He observed that one of the advantages of big data is how easy it is to get test data to validate a model that you built from sample data.

Ozimek notes that he is “for the most part a p-value checking, residual examining, data modeling culture economist,” but he’s correct to observe that if you can test your model on real data, then you should.

What I’ll describe is certainly not the only way to divide data in Minitab Statistical Software. Still, I think it’s pretty good if I do say so myself. Want...

Creating a Custom Report using Minitab, part 2

Now that you’ve seen how to automatically import data and run analyses in my previous post, let’s create the Monthly Report!

I will be using a Microsoft Word Document (Office 2010) and adding bookmarks to act as placeholders for the Graphs, statistics, and boilerplate conclusions.

Let’s go through the steps to accomplish this:

  • Open up an existing report that you have previously created in Microsoft Word.
  • Highlight a section of the document where you would like to place the created Minitab graph or statistic.
  • Go to the Insert tab, click the Bookmark link, and type in the name of what you will be...