Plaintiff Emily Rector appeals from a jury verdict of no cause of action in a products liability suit arising out of defendant’s sale to plaintiff of a burglar alarm system. We find it unnecessary to address the issue she raises because we conclude that she presented insufficient evidence to support a reasonable inference that the product contained a defect attributable to defendant. The case should therefore not have been submitted to the jury for decision.
Plaintiff’s proofs at trial were as follows. Plaintiff was a widow living alone in a neighborhood of Detroit which had recently been the scene of several burglaries and muggings. Since her job often caused her to return home later in the evenings, she became apprehensive about her safety. In February, 1971, plaintiff purchased a burglar alarm system for her home from defendant Michigan Security Systems, Inc. Having explained her concerns to Clem Campbell, defendant’s sales representative, and relying upon his recommendation, she also purchased a remote control panic sender device. This consisted of a small, hand-held unit with a push button which, when pressed within a limited range of plaintiff’s home, would transmit a radio signal activating a receiver in her attic. The receiver would then trigger a very loud siren and a flashing light on her roof.
Defendant installed the system in plaintiff’s home in March, 1971. Both plaintiff and defendant tested the system, including the sender device, and found it in satisfactory working order. However, *295the alarm did go off, apparently without cause, on at least one occasion two or three months after its installation. One of defendant’s installers checked the system the next day, but found nothing amiss. The installer surmised to plaintiff at the time that another object emitting stray radio frequency signals (e.g., a garage door opener, ham radio or a police car radio) might have triggered the alarm, but he otherwise deemed the system to be functioning properly.
Plaintiff experienced no further problems until November 18, 1971. She pulled into her driveway at 9:45 p.m., took the sender in hand, and then, upon opening her car door, sensed someone’s presence. Plaintiff immediately pressed the button on the sender, but the alarm system failed to function. As she continued to futilely press the button, she was dragged from her car and thrown to the ground. Her two assailants escaped with her purse. Plaintiff also sustained a seriously fractured ankle, requiring surgery, and has since suffered numerous complications. One of plaintiff’s neighbors verified that the alarm system had been turned on that day.
Joseph Matcher, a technician employed by Multi-Elmac Company, the manufacturer of plaintiff’s sender and third-party defendant in this case, testified that he had put his initials on a repair invoice indicating that plaintiff’s sender had been repaired on December 2, 1971. Clem Campbell, defendant’s sales representative, stated that both plaintiff’s sender and receiver had been replaced after November 18, 1971, and that he did not know what happened to the replaced sender. He also testified that he had tested the sender in plaintiff’s home after November 18, that it did not function at that time, and that Multi-Elmac had *296subsequently reported that the sender was "out of frequency”.
Phil Latona, the installer of plaintiffs system, testified that he had never tested the sender in plaintiffs car. He also admitted that he was not very familiar with the internal mechanism of the sender. Although he could tell whether it was functioning or not, he could not fully test it after installation to determine whether potential or latent defects existed. Plaintiff rested her case.
While plaintiff has the burden of proof to establish a defect attributable to defendant, we will also take into account the testimony offered by third-party defendant Multi-Elmac which, in certain respects, plaintiff relied on to establish her prima facie case. Joseph Matcher, Multi-Elmac’s repair technician, was recalled to testify regarding the repairs he had performed on plaintiffs sender.1 Based on the notations he had made in his repair invoice, he stated that he had found no workmanship defect. He had done a slight tuning adjustment to bring the sender closer to the standard frequency specification. But again according to the invoice, he testified that the sender was probably within frequency specifications because he would normally have noted any need for major adjustment. Matcher then stated that he had marked a column on the invoice entitled "component failure”, and that the notation might have referred to a defective battery in the sender. Matcher also testified that he had replaced the push button on the unit, but did not know whether the replacement was for esthetic reasons (e.gworn or dirty appearance) or because it was defective.
*297Finally, Peter Wallen, an electronics engineer from Multi-Elmac, testified extensively as to various factors affecting the functional capacity of the sender and receiver. He stated that atmospheric changes, other objects emitting radio signals, the metal of a car dashboard, the tinted glass of a car windshield and abusive treatment of the sender could all result in or contribute to desensitizing the receiver or interfering with the transmitting capacity of the sender. In his opinion, the sender must have been functioning correctly when it left the manufacturer or it would not have worked properly for eight months thereafter.
Plaintiff submitted her case to the jury on the theories of defendant’s negligence and of defendant’s breach of an implied warranty of reasonable fitness for the purpose intended. Under either theory, plaintiff must initially prove a defect attributable to the defendant. Piercefield v Remington Arms Co, Inc, 375 Mich 85, 98-99; 133 NW2d 129 (1965), Snider v Bob Thibodeau Ford, Inc, 42 Mich App 708, 713; 202 NW2d 727 (1972), Caldwell v Fox, 394 Mich 401, 410; 231 NW2d 46 (1975).
Although the proofs suggest a number of possible causes for malfunction of the sender, plaintiff never sought to pinpoint the specific nature of the alleged defect. This is, however, not necessarily fatal to her case if one could reasonably infer from circumstantial evidence that a defect did exist. See Kujawski v Cohen, 56 Mich App 533; 224 NW2d 908 (1974), Bronson v J L Hudson Co, 376 Mich 98; 135 NW2d 388 (1965), Piper v Tensor Corp, 71 Mich App 658; 248 NW2d 659 (1976), Garmo v General Motors Corp, 45 Mich App 703; 207 NW2d 146 (1973).
We also preliminarily note that we must view the evidence in the light most favorable to the *298plaintiff. If there is any competent evidence sufficient to support a verdict for plaintiff, we may not interfere with the province of the trier of fact. See Kujawski, supra, at 535-538. The comparative probability or plausibility of competing theories is not for this Court or a trial court to decide. Holloway v General Motors Corp (On Rehearing), 403 Mich 614; 271 NW2d 777 (1978), rev’g 399 Mich 617; 250 NW2d 736 (1977).
Plaintiff sufficiently established that the sender malfunctioned on the date of her injury, and that it was still nonfunctional when defendant’s employees later checked the alarm system at her home. Proofs were also adduced that thereafter her alarm system only operated properly by remote control when the sender was replaced, that both the battery and the push button of plaintiff’s sender were replaced, and that the sender required adjustment to frequency specifications after the initial date of malfunction. Although the nature of the specific defect is not clear, one may reasonably infer that either one cause alone, or a combination of causes, rendered the plaintiff’s sender defective on November 18, 1971.
However, one cannot reasonably infer that any of the aforementioned possible defects is attributable to defendant. Plaintiff stated that the alarm system, including the sender, worked properly from the date of installation until the date of her injury, a period of some eight months. The one possible exception was a false alarm about two or three months after installation. But the only explanation offered was that a stray radio signal had activated the receiver. Plaintiff made no showing that the receiver was defective then or on November 18, 1971. If anything, the false alarm seems to attest to the sensitivity of the receiver. In addition, *299this incident cannot be linked to the operation or malfunction of the sender and is thus not probative of any existing defect in that unit. Compare, Snider, supra, Piper, supra, and Garmo, supra, in which a history of repairs to or of difficulties with the alleged defective part aided in establishing a link between defendant and the defect.
If the sender functioned appropriately for eight months without evidence of defect, one must then be able to reasonably infer that the defect or defects revealed by the later malfunction were latent in the product at the time the defendant sold it to plaintiff. See Holloway, supra. The mere fact of malfunction does not give rise to any necessary inference as to when the defect arose.
Third-party defendant’s repair technician testified that the sender’s battery and push button were replaced, and that he adjusted the unit to meet frequency specifications. Batteries are not components which one would expect to function indefinitely. They are subject to wear, must be replaced periodically, and are not evidence of a latent defect attributable to defendant. As for the push button, it was unclear whether the part was replaced because it was actually defective or merely worn in appearance. While one might reasonably infer that it was broken at the time of repair, there is no showing as to why, how or when the push button might have been damaged. The connection between a possibly defective push button in December, 1971, the cause of which defect in any case remains unknown, and the existence of a defect in March, 1971, attributable to defendant is tenuous in the extreme.2 See Kup*300kowski v Avis Ford, Inc, 395 Mich 155; 235 NW2d 324 (1975), aff'g 51 Mich App 668; 215 NW2d 767 (1974).
Neither will the tuning of the sender to meet frequency specifications support a finding of a defect attributable to defendant. The repair technician testified that he most probably only made a slight tuning adjustment to meet more closely the standard sender frequency specifications and that the sender was probably within the appropriate frequency range because he would have noted any necessity for major adjustment on the repair invoice. It is of course possible to infer that the sender was sufficiently "out of frequency” to malfunction on the date of plaintiffs injury or that the variance from standard frequency contributed to the failure of the alarm system. But again, any further inference as to the existence of such a defect in March, 1971, is purely speculative and not supported by proofs at trial. See Meli v General Motors Corp, 37 Mich App 514; 195 NW2d 85 (1972).
Regarding other reasons offered by Multi-Elmac’s expert witness for malfunction of the sender, including atmospheric variations and other types of interference with transmission of the signal, they were simply conjectural and not shown to be linked to the particular malfunction of plaintiffs sender. We conclude from the above analysis that plaintiff did not sustain her burden of introducing evidence from which the jury could reasonably infer that any defect in the sender existed at the time it left defendant’s control.
Affirmed. Costs to defendant.
*301D. C. Riley, J., concurred.Matcher testified that, at the time he made the repairs on plaintiffs sender, he was unaware of the circumstances under which it had failed to function. Neither did he know that a lawsuit would later be filed on the basis of alleged defects in the sender.
Plaintiff argued below that the push button might possibly have been broken when she, in her panic, pressed it hard and repeatedly in an attempt to activate the alarm system. Plaintiff further contended that this theory would support a conclusion of lack of reasonable *300fitness of the product for the purpose intended. While we concede the theoretical possibility of plaintiffs contention, we nevertheless emphasize that one must speculate on the basis of an inference to even reach a conclusion as to the cause of any damage to the push button.