Don Johnston

Mathematical Expressions Problem Fixed

Mathematical expressions are now displayed. A WordPress update had stopped mathematical expressions from being displayed by the plugin which I had been using for that purpose. I replaced that plugin with one which appears to be kept up to date. As a result, the problem appears to have been fixed. I will now resume publishing. […]

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Don Johnston

Mathematical Expressions Not Displayed

Mathematical expressions are not displayed in this blog at present. The problem is that the plugin used for displaying them is not compatible with the latest version of WordPress. I am currently looking for a solution to that problem. I won’t be publishing any more posts until the problem is fixed. Please check again in […]

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dreamstime_xs_81508346

Data Accuracy

Introduction Achieving good inventory management requires reliable accurate up to date data. If there are problems with data accuracy, check to see that your inventory system (or ERP system) is being used as it is designed to be used. If you try to shortcut data entry processes because the methods described in the user manual […]

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Purchase order

Reducing Ordering Delays

Introduction The lead time for an item starts when the item should be ordered, not when the order is sent to the supplier. To find out the effect on the required investment in inventory of that time difference, see the table in the article entitled “Reducing Lead Times”. If a periodic review replenishment system is […]

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Croston Median

Demand Rate Estimation

Introduction If there is no evidence of trend or seasonal effects then forecasting using demand history alone usually simply involves estimation of the demand rate (mean demand per unit time). All of the algorithms mentioned in this article can be used as a basis for forecasting involving trend and seasonal effects. The performance of each […]

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Purchase order

What is Optimal Replenishment?

Introduction Claims that particular software packages provide optimal inventory management are commonplace. Such claims, by themselves, are meaningless. They only become meaningful if there is a full description of the theoretical assumptions involved and of the objective function (whatever is to be minimised or maximised).   Total Cost as the Objective Function Total cost is […]

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Effects of relatively high demands on ordering

Evaluating Forecasting Algorithms

Introduction In order to determine when and how much of an item to order, it is necessary to have a forecast of customer demands. The human brain is not as good as appropriate statistical analysis at interpreting statistical data. Forecasting of customer demands using demand history alone is, therefore, better done by a computer using […]

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peas

ABC Analysis

Pareto Principle The Pareto Principle is named after an Italian economist Vilfredo Pareto who noticed that 80% of the peas which he grew in his garden came from about 20% of the pods. He also found that, in most countries, about 20% of the population owns 80% of the land. Those observations lead to what […]

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