History of Normal Distribution
History of the Normal Distribution Author(s) David M. Lane Prerequisites Distributions, Central Tendency, Variability, Binomial Distribution In the chapter on probability, we saw that the binomial distribution could be used to solve problems such as "If a fair coin is flipped 100 times, what is the probability of getting 60 or more heads?" where x is the number of heads (60), N is the number of flips (100), and π is the probability of a head (0.5). Abraham de Moivre, an 18th century statistician and consultant to gamblers, was often called upon to make these lengthy computations. de Moivre noted that when the number of events (coin flips) increased, the shape of the binomial distribution approached a very smooth curve. Figure 1. de Moivre reasoned that if he could find a mathematical expression for this curve, he would be able to solve problems such as finding the probability of 60 or more heads out of 100 coin flips much more easily. Figure 2.
Sears And Kmart Will Close At Least 50 Stores After Poor Holiday Sales
Sears and its subsidiary Kmart recently announced plans to close at least 50 stores sooner than expected. Reportedly, the original plan was to close unprofitable stores over the coming months. But the rush to close this group now makes some sense. Sears' stock has been hovering around a 12-year-low, and its expected fourth quarter total revenue is almost a billion dollars lower than the year before. And compared to major department stores like J.C. In fact, many Wall Street analysts reportedly don't even track Sears anymore. Last year, to gain funds, Sears sold assets like Sears Canada and Lands' End. This video includes clips from Lands' End and Sears and images from Getty Images. We'll find the stories you care about and deliver them on your schedule.
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The T-Test
The t-test assesses whether the means of two groups are statistically different from each other. This analysis is appropriate whenever you want to compare the means of two groups, and especially appropriate as the analysis for the posttest-only two-group randomized experimental design. Figure 1 shows the distributions for the treated (blue) and control (green) groups in a study. Actually, the figure shows the idealized distribution – the actual distribution would usually be depicted with a histogram or bar graph. The figure indicates where the control and treatment group means are located. What does it mean to say that the averages for two groups are statistically different? This leads us to a very important conclusion: when we are looking at the differences between scores for two groups, we have to judge the difference between their means relative to the spread or variability of their scores. The formula for the t-test is a ratio. SE(XˉT−XˉC)=nTvarT+nCvarC
Watch: Is masturbation good for you?
First up, let's just be honest - 95 percent of men and 72 percent of women reading this are just here to feel good about what you're already doing behind closed doors (hopefully). But if the rest of you have been holding out your entire lives, just waiting for science to give you a reason to enjoy your alone time a little too much, it's time to cancel your plans and get down to it, because according to the latest episode of AsapSCIENCE, you're doing yourself no favours by... doing yourself no favours. Despite rumours that masturbation can lead to infertility and even blindness, research has shown that it's actually got a whole lot going for it. On a very basic level, it releases dopamine - a neurotransmitter that activates the 'pleasure centre' in your brain, and endorphins that actively decrease your perception of pain. Men in particular seem to benefit the most, with high ejaculation frequency correlating with a decreased risk of prostate cancer, says the video above.
Linear Equations
A linear equation is an equation for a straight line These are all linear equations: Let us look more closely at one example: Example: y = 2x+1 is a linear equation: The graph of y = 2x+1 is a straight line When x increases, y increases twice as fast, hence 2x When x is 0, y is already 1. Here are some example values: Check for yourself that those points are part of the line above! Different Forms There are many ways of writing linear equations, but they usually have constants (like "2" or "c") and must have simple variables (like "x" or "y"). Examples: These are linear equations: But the variables (like "x" or "y") in Linear Equations do NOT have: Examples: These are NOT linear equations: Slope-Intercept Form The most common form is the slope-intercept equation of a straight line: Example: y = 2x + 1 (Our example from the top, which is in Slope-Intercept form) Slope: m = 2 Intercept: b = 1 Point-Slope Form Another common one is the Point-Slope Form of the equation of a straight line: x1 = 2 y1 = 3 m = ¼
ONE-WAY ANOVA
Analysis of variance (ANOVA) for comparing means of three or more variables. Use this test for comparing means of 3 or more samples/treatments, to avoid the error inherent in performing multiple t-tests Background. Ideally, for this test we would have the same number of replicates for each treatment, but this is not essential. An important assumption underlies the Analysis of Variance: that all treatments have similar variance. Procedure (see worked example) Don't be frightened by this! Assume that we have recorded the biomass of 3 bacteria in flasks of glucose broth, and we used 3 replicate flasks for each bacterium. Step 1. Step 2. , S x2, and Sd2 (click here for method) Step 3. Step 4. Step 5. and call the sum B. Step 6. Step 7. Step 8. Step 9. Step 10. Step 11. [The total df is always one fewer than the total number of data entries] Step 12. F = Between treatments mean square / Residual mean square Step 13. What does all this mean? Analysis of variance: worked example D = (Grand total)2
Machine vs. Marketer — Who Reigns Supreme?
Being a digital marketer is an exciting gig. Ad platforms, best practices and tools change at warp speed, meaning you’re always learning and you’re never bored. But it’s a tough gig, too. In 2004, the internet became the highest grossing channel in advertising expenditure, and it’s been on the rise ever since. That up-and-to-the-right blue line means that acquisition has become more competitive than ever. Couple this with a rising average cost per click and cost per conversion, and you’ve got a hefty task at hand: Cut through the search noise, create a compelling digital experience and interpret and apply tens of thousands of data points all while coming in under budget. Yikes! It’s no wonder that marketers are looking at advances in automation, machine learning and artificial intelligence and asking, “What’s in it for me?” And while some see the “rise of the machines” as a threat, Mitch Joel, President of global digital agency Mirum, sees it as an opportunity: Machine vs. Kidding!
