F.TEST Function in Excel: Are Two Spreads Different?
F.TEST checks whether two samples have different variances — for instance, before choosing T.TEST type 2 or 3.
Read article →Linear Regression From Scratch in Python: How a Model Actually Learns
Linear Regression From Scratch in Python: How a Model Actually Learns
Code linear regression with gradient descent in plain NumPy, watch the model learn slope and intercept, then check it against NumPy and scikit-learn. The…
Read article →A Neural Network From Scratch in 30 Lines of NumPy
A Neural Network From Scratch in 30 Lines of NumPy
Build and train a two-layer neural network in plain NumPy to solve XOR — forward pass, backpropagation and gradient descent explained line by line.
Read article →T.INV.2T Function in Excel: Critical t Value
T.INV.2T Function in Excel: Critical t Value
T.INV.2T returns the t value for a two-tailed test — the multiplier for a confidence interval on a small sample.
Read article →T.DIST Function in Excel: Student’s t Probability
T.DIST Function in Excel: Student’s t Probability
T.DIST gives probabilities for the t-distribution — used instead of the normal curve when samples are small.
Read article →FORECAST.ETS.SEASONALITY Function in Excel: Which Cycle Did Excel Find?
FORECAST.ETS.SEASONALITY Function in Excel: Which Cycle Did Excel Find?
FORECAST.ETS.SEASONALITY reports the season length Excel detected — 12 for a yearly cycle in monthly data, 7 for a weekly cycle in daily data.
Read article →FORECAST.ETS.CONFINT Function in Excel: How Uncertain Is the Forecast?
FORECAST.ETS.CONFINT Function in Excel: How Uncertain Is the Forecast?
FORECAST.ETS.CONFINT returns the ± interval around a FORECAST.ETS value. A forecast of 1,200 ± 400 tells a very different story from 1,200 ± 40.
Read article →STEYX Function in Excel: Typical Error of a Trend Line
STEYX Function in Excel: Typical Error of a Trend Line
STEYX returns the standard error of predicted y values — roughly how far actual points sit from the trend line.
Read article →LOGEST Function in Excel: Exponential Curve Fit
LOGEST Function in Excel: Exponential Curve Fit
LOGEST fits y = b·mˣ and returns m (the growth factor) and b. m of 1.05 means 5% growth per period.
Read article →LINEST Function in Excel: Full Regression Statistics
LINEST Function in Excel: Full Regression Statistics
LINEST fits a straight line (or a multiple regression) and returns slope, intercept and, optionally, R², standard errors and more — an entire regression…
Read article →HARMEAN Function in Excel: The Right Average for Rates
HARMEAN Function in Excel: The Right Average for Rates
HARMEAN averages rates properly. Drive 60 km/h one way and 40 km/h back, and your average speed is 48, not 50.
Read article →Slow Wi-Fi at Home? 10 Fixes That Actually Work
Slow Wi-Fi at Home? 10 Fixes That Actually Work
Diagnose and fix slow home Wi-Fi: speed tests the right way, router placement, 2.4 GHz vs 5 GHz, channel congestion, DNS, restarting, firmware, mesh…
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